Deprecated Series.ftype, Series.ftypes and DataFrame.ftypes features
Deprecation of `Series.ftype`, `Series.ftypes` and `DataFrame.ftypes` 
closes #26705

- [x] Updated the docstrings for the sphinx documentation
- [x] Updated the unit tests for testing deprecation warnings 
- [x] Added Git Issue Number to unit tests
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26751?src=pr&el=h1) Report
> Merging [#26751](https://codecov.io/gh/pandas-dev/pandas/pull/26751?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/c7748ca057cad4a80a6c4cbf8b49c5d9f3e7ea1c?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26751/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26751?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #26751      +/-   ##
==========================================
- Coverage    91.7%   91.69%   -0.01%     
==========================================
  Files         179      179              
  Lines       50767    50770       +3     
==========================================
- Hits        46555    46554       -1     
- Misses       4212     4216       +4
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.29% <100%> (ø)` | :arrow_up: |
| #single | `41.2% <0%> (-0.09%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26751?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/26751/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `93.62% <100%> (+0.01%)` | :arrow_up: |
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/26751/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `93.64% <100%> (ø)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/26751/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `78.94% <0%> (-10.53%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/26751/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.88% <0%> (-0.12%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26751?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/26751?src=pr&el=footer). Last update [c7748ca...2c80a30](https://codecov.io/gh/pandas-dev/pandas/pull/26751?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 I can see that the builds are failing. Upon having a close look at the build logs, I can see that these failures are coming from the following test functions:

- `test_empty_frame_dtypes_ftypes` (pandas/tests/frame/test_dtypes.py)
- `test_concat_empty_series_dtypes` (pandas/tests/series/test_combine_concat.py)
- `test_construct_DataFrame_with_sp_series` (pandas/tests/sparse/series/test_series.py)


Do you want me to update those unit tests as well? there is no need to create a new PR for changes; just push to the old one

since it’s already done it’s ok