DOC: Removed Timedelta.is_populated and fixed spelling errors
- [x] closes #17369 
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

Additional fixes per comments in #17424 
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17469?src=pr&el=h1) Report
> Merging [#17469](https://codecov.io/gh/pandas-dev/pandas/pull/17469?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/ee6185e2fb9461632949f3ba52a28b37a1f7296e?src=pr&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17469/graphs/tree.svg?src=pr&width=650&token=eZ4WkYLtcO&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/17469?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17469      +/-   ##
==========================================
- Coverage   91.16%   91.14%   -0.02%     
==========================================
  Files         163      163              
  Lines       49590    49590              
==========================================
- Hits        45209    45200       -9     
- Misses       4381     4390       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.93% <ø> (ø)` | :arrow_up: |
| #single | `40.25% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17469?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17469?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17469?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.72% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17469?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/17469?src=pr&el=footer). Last update [ee6185e...5398d4d](https://codecov.io/gh/pandas-dev/pandas/pull/17469?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks!