Remove incorrect line in Series init docstring

[petern48]

• closes DOC: Series.__init__ doc incorrectly says dtype is ignored if data is a Series #61848
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.

Copied over from the issue for convenience

    dtype : str, numpy.dtype, or ExtensionDtype, optional
        Data type for the output Series. If not specified, this will be
        inferred from `data`.
        See the :ref:`user guide <basics.dtypes>` for more usages.
        If ``data`` is Series then is ignored.

The last line here is incorrect. specifying a dtype will override the default behavior. See this example

>>> import pandas as pd
>>> ser = pd.Series([1,2,3])
>>> ser
0    1
1    2
2    3
dtype: int64
>>> pd.Series(ser, dtype=float)
0    1.0
1    2.0
2    3.0
dtype: float64

[jbrockmendel]

thanks @petern48