Remove Panel References from Tests
ref #25632 this removes a good deal of Panel references from tests though not all (excluding anything for msgpack). 

I think after this and #25567 get merged we can starting finalizing the Panel removal and get out of docs as well
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26332?src=pr&el=h1) Report
> Merging [#26332](https://codecov.io/gh/pandas-dev/pandas/pull/26332?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/ee6b1318ff07806ead79dac8119ad9ce580afe1c?src=pr&el=desc) will **decrease** coverage by `0.24%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26332/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26332?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #26332      +/-   ##
==========================================
- Coverage   92.04%    91.8%   -0.25%     
==========================================
  Files         175      175              
  Lines       52297    52297              
==========================================
- Hits        48137    48011     -126     
- Misses       4160     4286     +126
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.35% <ø> (-0.24%)` | :arrow_down: |
| #single | `40.72% <ø> (-0.15%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26332?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/panel.py](https://codecov.io/gh/pandas-dev/pandas/pull/26332/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcGFuZWwucHk=) | `17.49% <0%> (-17.65%)` | :arrow_down: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/26332/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `78.94% <0%> (-10.53%)` | :arrow_down: |
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/26332/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `93.34% <0%> (-0.24%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/26332/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.01% <0%> (-0.12%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26332?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26332?src=pr&el=footer). Last update [ee6b131...729edea](https://codecov.io/gh/pandas-dev/pandas/pull/26332?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26332?src=pr&el=h1) Report
> Merging [#26332](https://codecov.io/gh/pandas-dev/pandas/pull/26332?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/ee6b1318ff07806ead79dac8119ad9ce580afe1c?src=pr&el=desc) will **decrease** coverage by `0.24%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26332/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26332?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #26332      +/-   ##
==========================================
- Coverage   92.04%    91.8%   -0.25%     
==========================================
  Files         175      175              
  Lines       52297    52297              
==========================================
- Hits        48137    48011     -126     
- Misses       4160     4286     +126
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.35% <ø> (-0.24%)` | :arrow_down: |
| #single | `40.72% <ø> (-0.15%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26332?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/panel.py](https://codecov.io/gh/pandas-dev/pandas/pull/26332/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcGFuZWwucHk=) | `17.49% <0%> (-17.65%)` | :arrow_down: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/26332/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `78.94% <0%> (-10.53%)` | :arrow_down: |
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/26332/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `93.34% <0%> (-0.24%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/26332/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.01% <0%> (-0.12%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26332?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26332?src=pr&el=footer). Last update [ee6b131...729edea](https://codecov.io/gh/pandas-dev/pandas/pull/26332?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 looks ok, pending CI build issues. thanks @WillAyd 