BUG: Allow pd.unique to accept tuple of strings
 - [x] tests added / passed
 - [x] passes ``git diff upstream/master -u -- "*.py" | flake8 --diff``
 - [x] whatsnew entry

xref #17077

 `pd.unique()` calls `_ensure_arraylike` which did not accept tuples that contains strings. Converts tuple to list first before dispatching to `list_to_object_array`
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17108?src=pr&el=h1) Report
> Merging [#17108](https://codecov.io/gh/pandas-dev/pandas/pull/17108?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/465c59f964c8d71d8bedd16fcaa00e4328177cb1?src=pr&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17108/graphs/tree.svg?width=650&src=pr&token=eZ4WkYLtcO&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/17108?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17108      +/-   ##
==========================================
- Coverage   91.02%   91.01%   -0.02%     
==========================================
  Files         161      161              
  Lines       49397    49399       +2     
==========================================
- Hits        44966    44959       -7     
- Misses       4431     4440       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.78% <100%> (ø)` | :arrow_up: |
| #single | `40.28% <0%> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17108?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/algorithms.py](https://codecov.io/gh/pandas-dev/pandas/pull/17108?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYWxnb3JpdGhtcy5weQ==) | `94.15% <100%> (+0.01%)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17108?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17108?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.66% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17108?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/17108?src=pr&el=footer). Last update [465c59f...822a4dc](https://codecov.io/gh/pandas-dev/pandas/pull/17108?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 other that the doc changes suggested by @gfyoung this lgtm. @mroeschke : Thanks!  Will merge on green. Thanks @mroeschke !