DOC: Update Series.repeat docstring

[pedropazzini]

Checklist for the pandas documentation sprint (ignore this if you are doing
an unrelated PR):

• [ X] PR title is "DOC: update the docstring"
• The validation script passes: scripts/validate_docstrings.py <your-function-or-method>
• [ X] The PEP8 style check passes: git diff upstream/master -u -- "*.py" | flake8 --diff
• [ X] The html version looks good: python doc/make.py --single <your-function-or-method>
• [ X] It has been proofread on language by another sprint participant

Please include the output of the validation script below between the "```" ticks:

################################################################################
####################### Docstring (pandas.Series.repeat) #######################
################################################################################

Repeat elements of a Series.

Each element of the Series is repeated 'repeats' times.

Parameters
----------
repeats : int
    The number of repetitions for each element.
*args
    These parameters will be passed to a validation function.
**kwargs
    These parameters will be passed to a validation function.

See also
--------
Series.append : Concatenate two or more Series.
pandas.concat : Concatenate two or more DataFrames.
numpy.repeat : Repeat elements of an array.

Returns
-------
Series
    The repeated version of the Series.

Examples
--------
>>> df = pd.DataFrame({'col1' : ['A','B','C'],'col2' : [ 0 , 1 , 2 ]})
>>> df
col1  col2
0    A     0
1    B     1
2    C     2
>>> df.col1.repeat(3)
0    A
0    A
0    A
1    B
1    B
1    B
2    C
2    C
2    C
Name: col1, dtype: object

################################################################################
################################## Validation ##################################
################################################################################

Errors found:
	Errors in parameters section
		Parameters {'kwargs', 'args'} not documented
		Unknown parameters {'**kwargs', '*args'}
		Parameter "*args" has no type
		Parameter "**kwargs" has no type

The errors returned for the script is an error, since t is not ready for **kwargs and *args parameters.

[jorisvandenbossche]

@pedropazzini Can you check the similar PR #19985 to see if there is something in there you can use? (eg explanation for the **kwargs)

[TomAugspurger]

Single backtick for parameters like `repeats`

[TomAugspurger]

You can remove args and kwargs. The validation function is an implementation detail that users shouldn't have to worry about. repeats is the only valid argument.

You could mention, perhaps in Notes that "unlike numpy.repeat, `axis` is not a valid argument".

[TomAugspurger]

Listen to @jorisvandenbossche about args and kwargs, not me :)

[jorisvandenbossche]

After discussion, you can document them like

*args, **kwargs
    Additional keywords have no effect but might be accepted for
    compatibility with numpy.

[TomAugspurger]

Spacing looks off. Should move it over a few spaces I think. Double check that this is right.

[jorisvandenbossche]

@pedropazzini Is there a reason that you closed this?