Remove flake8-rst usage (#51847)

Removed flake8-rst since it is not maintained and breaks with python3.10, with last update on 2020.

Co-authored-by: Marco Edward Gorelli <[email protected]>

Author: ErdiTk

setup.cfg

@@ -33,35 +33,3 @@ exclude =
     versioneer.py,
     # exclude asv benchmark environments from linting
     env
-
-[flake8-rst]
-max-line-length = 84
-bootstrap =
-    import numpy as np
-    import pandas as pd
-    # avoiding error when importing again numpy or pandas
-    np
-    # (in some cases we want to do it to show users)
-    pd
-ignore =
-    # space before : (needed for how black formats slicing)
-    E203,
-    # module level import not at top of file
-    E402,
-    # line break before binary operator
-    W503,
-    # Classes/functions in different blocks can generate those errors
-    # expected 2 blank lines, found 0
-    E302,
-    # expected 2 blank lines after class or function definition, found 0
-    E305,
-    # We use semicolon at the end to avoid displaying plot objects
-    # statement ends with a semicolon
-    E703,
-    # comparison to none should be 'if cond is none:'
-    E711,
-exclude =
-    doc/source/development/contributing_docstring.rst,
-    # work around issue of undefined variable warnings
-    # https://github.com/pandas-dev/pandas/pull/38837#issuecomment-752884156
-    doc/source/getting_started/comparison/includes/*.rst