Update series.py
Added drop_duplicates_index function to base series object. very useful when working with time series.

- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [ ] whatsnew entry

Hello @Omerdan03! Thanks for opening this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:

* In the file [`pandas/core/series.py`](https://github.com/pandas-dev/pandas/blob/a39287bbde5bd897093189b697a5f939bd952db0/pandas/core/series.py):

> [Line 2144:1](https://github.com/pandas-dev/pandas/blob/a39287bbde5bd897093189b697a5f939bd952db0/pandas/core/series.py#L2144): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace
> [Line 2147:1](https://github.com/pandas-dev/pandas/blob/a39287bbde5bd897093189b697a5f939bd952db0/pandas/core/series.py#L2147): [W293](https://duckduckgo.com/?q=pep8%20W293) blank line contains whitespace

