Fix broken/deprecated documentation links in MEPs and testing guides (matplotlib#30343)

* Fixed broken links

* Minor changes

* Made requested changes

* Update doc/devel/MEP/MEP10.rst

Co-authored-by: Ruth Comer <[email protected]>

---------

Co-authored-by: Ruth Comer <[email protected]>

Author: nrnavaneet

doc/devel/MEP/MEP10.rst

@@ -44,8 +44,7 @@ these new features.
 Numpy docstring format
 ----------------------
 
-`Numpy docstring format
-<https://github.com/numpy/numpy/blob/master/doc/HOWTO_DOCUMENT.rst.txt>`_:
+`Numpy docstring format <https://numpydoc.readthedocs.io/en/stable/format.html>`_:
 This format divides the docstring into clear sections, each having
 different parsing rules that make the docstring easy to read both as
 raw text and as HTML.  We could consider alternatives, or invent our

doc/devel/MEP/MEP11.rst

@@ -130,7 +130,7 @@ ordered from best/hardest to worst/easiest):
 1. The distutils wininst installer allows a post-install script to
    run.  It might be possible to get this script to run pip_ to
    install the other dependencies.  (See `this thread
-   <http://grokbase.com/t/python/distutils-sig/109bdnfhp4/distutils-ann-setuptools-post-install-script-for-bdist-wininst>`_
+   <https://mail.python.org/pipermail/distutils-sig/2010-September/016857.html>`_
    for someone who has trod that ground before).
 
 2. Continue to ship dateutil_, pytz_, six_ and pyparsing_ in
@@ -177,4 +177,4 @@ out of the box.
 .. _pytz: https://pypi.org/project/pytz/
 .. _setuptools: https://pypi.org/project/setuptools/
 .. _six: https://pypi.org/project/six/
-.. _easy_install: https://setuptools.readthedocs.io/en/latest/easy_install.html
+.. _easy_install: https://setuptools.pypa.io/en/latest/deprecated/easy_install.html

doc/devel/testing.rst

@@ -274,14 +274,15 @@ You can also run tox on a subset of environments:
 
     $ tox -e py310,py311
 
-Tox processes everything serially so it can take a long time to test
-several environments. To speed it up, you might try using a new,
-parallelized version of tox called ``detox``. Give this a try:
+Tox processes environments sequentially by default,
+which can be slow when testing multiple environments.
+To speed this up, tox now includes built-in parallelization support
+via the --parallel flag. Give it a try:
 
 .. code-block:: bash
 
-    $ pip install -U -i http://pypi.testrun.org detox
-    $ detox
+    $ tox --parallel auto
+
 
 Tox is configured using a file called ``tox.ini``. You may need to
 edit this file if you want to add new environments to test (e.g.,