[3.13] Docs(build): linklint is now called sphinx_linklint (GH-156373)

* Docs(build): linklint is now called sphinx_linklint

* Docs(build): move the lock command to the Makefile

* Update Doc/Makefile

Co-authored-by: Stan Ulbrych <stan@python.org>

* Add a comment clarify cooldown (and excludes) and add to `make help`

---------
(cherry picked from commit 98bd716)

Co-authored-by: Ned Batchelder <ned@nedbatchelder.com>
Co-authored-by: Stan Ulbrych <stan@python.org>

Author: nedbat

Doc/conf.py

@@ -39,7 +39,7 @@
 
 # Skip if downstream redistributors haven't installed them
 _OPTIONAL_EXTENSIONS = (
-    'linklint.ext',
+    'sphinx_linklint.ext',
     'notfound.extension',
     'sphinxext.opengraph',
 )

Doc/requirements.txt

@@ -11,13 +11,12 @@ sphinx<9.0.0
 
 blurb
 
-sphinxext-opengraph~=0.13.0
+sphinx-linklint
 sphinx-notfound-page~=1.0.0
+sphinxext-opengraph~=0.13.0
 
 # The theme used by the documentation is stored separately, so we need
 # to install that as well.
 python-docs-theme>=2023.3.1,!=2023.7
 
-linklint
-
 -c constraints.txt