DOC: update the Period.dayofweek attribute docstring
Checklist for the pandas documentation sprint (ignore this if you are doing
an unrelated PR):

- [x] PR title is "DOC: update the <your-function-or-method> docstring"
- [x] 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:

```
(pandas_dev) root@kalih:~/pythonpanda/pandas# python scripts/validate_docstrings.py pandas.Period.dayofweek

################################################################################
##################### Docstring (pandas.Period.dayofweek)  #####################
################################################################################

Return the day of the week.

This attribute returns the day of the week on which the particular
starting date for the given period occurs with Monday=0, Sunday=6.

Returns
-------
Int
    Range of 0 to 6

See also
--------
Period.dayofyear
    Return the day of year.
Period.daysinmonth
    Return the days in that month.

Examples
--------
>>> period1 = pd.Period('2012-1-1 19:00', freq='H')
>>> period1
Period('2012-01-01 19:00', 'H')
>>> period1.dayofweek
6

>>> period2 = pd.Period('2013-1-9 11:00', freq='H')
>>> period2
Period('2013-01-09 11:00', 'H')
>>> period2.dayofweek
2

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

Docstring for "pandas.Period.dayofweek" correct. :)
```

If the validation script still gives errors, but you think there is a good reason
to deviate in this case (and there are certainly such cases), please state this
explicitly.

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/20280?src=pr&el=h1) Report
> :exclamation: No coverage uploaded for pull request base (`master@fb556ed`). [Click here to learn what that means](https://docs.codecov.io/docs/error-reference#section-missing-base-commit).
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/20280/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/20280?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##             master   #20280   +/-   ##
=========================================
  Coverage          ?    91.7%           
=========================================
  Files             ?      150           
  Lines             ?    49168           
  Branches          ?        0           
=========================================
  Hits              ?    45090           
  Misses            ?     4078           
  Partials          ?        0
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.09% <ø> (?)` | |
| #single | `41.86% <ø> (?)` | |


------

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> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/20280?src=pr&el=footer). Last update [fb556ed...de15589](https://codecov.io/gh/pandas-dev/pandas/pull/20280?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @hammadmashkoor Thanks a lot! Thanks @jorisvandenbossche 