CLN: remove values attribute from datetimelike EAs
We don't need a `.values` attribute on the EAs (in the interface, we actually explicitly disallow it (in words and tests)). 

I thought there was a reason during the PeriodArray PR that this couldn't yet be removed, but relevant tests seem to be passing locally.

cc @jbrockmendel 
Hello @jorisvandenbossche! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/core/arrays/datetimelike.py`](https://github.com/jorisvandenbossche/pandas/blob/35c4708c714ff0efb5c5657ef1d032cef912e3d3/pandas/core/arrays/datetimelike.py) !

 - There are no PEP8 issues in the file [`pandas/core/arrays/datetimes.py`](https://github.com/jorisvandenbossche/pandas/blob/35c4708c714ff0efb5c5657ef1d032cef912e3d3/pandas/core/arrays/datetimes.py) !

 - There are no PEP8 issues in the file [`pandas/core/arrays/timedeltas.py`](https://github.com/jorisvandenbossche/pandas/blob/35c4708c714ff0efb5c5657ef1d032cef912e3d3/pandas/core/arrays/timedeltas.py) !

 - There are no PEP8 issues in the file [`pandas/core/indexes/datetimes.py`](https://github.com/jorisvandenbossche/pandas/blob/35c4708c714ff0efb5c5657ef1d032cef912e3d3/pandas/core/indexes/datetimes.py) !

 LGTM.  Are there PeriodArray tests there were disabled that can now be un-disabled? > LGTM. Are there PeriodArray tests there were disabled that can now be un-disabled?

Yes, good catch. # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23603?src=pr&el=h1) Report
> Merging [#23603](https://codecov.io/gh/pandas-dev/pandas/pull/23603?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/f6917110611dcd1978286419529a85eca293fd00?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `80%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23603/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23603?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #23603      +/-   ##
==========================================
- Coverage   92.25%   92.25%   -0.01%     
==========================================
  Files         161      161              
  Lines       51262    51260       -2     
==========================================
- Hits        47292    47290       -2     
  Misses       3970     3970
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.63% <80%> (-0.01%)` | :arrow_down: |
| #single | `42.33% <60%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/23603?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/arrays/timedeltas.py](https://codecov.io/gh/pandas-dev/pandas/pull/23603/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3RpbWVkZWx0YXMucHk=) | `93.78% <100%> (ø)` | :arrow_up: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/23603/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `96.13% <100%> (ø)` | :arrow_up: |
| [pandas/core/arrays/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/23603/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lcy5weQ==) | `98.42% <100%> (ø)` | :arrow_up: |
| [pandas/core/arrays/datetimelike.py](https://codecov.io/gh/pandas-dev/pandas/pull/23603/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lbGlrZS5weQ==) | `95.9% <50%> (-0.03%)` | :arrow_down: |
| [pandas/core/accessor.py](https://codecov.io/gh/pandas-dev/pandas/pull/23603/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYWNjZXNzb3IucHk=) | `98.79% <0%> (ø)` | :arrow_up: |
| [pandas/core/missing.py](https://codecov.io/gh/pandas-dev/pandas/pull/23603/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvbWlzc2luZy5weQ==) | `91.7% <0%> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23603?src=pr&el=continue).
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> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23603?src=pr&el=footer). Last update [f691711...b303239](https://codecov.io/gh/pandas-dev/pandas/pull/23603?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
