[3.0.x] Refs #25778 -- Updated sphinx-doc.org links to HTTPS.

Backport of 32166a9f7c from master.

docs/README

@@ -14,4 +14,4 @@ To create an HTML version of the docs:
 The documentation in _build/html/index.html can then be viewed in a web browser.
 
 [1] http://docutils.sourceforge.net/rst.html
-[2] http://sphinx-doc.org/
+[2] https://www.sphinx-doc.org/

docs/conf.py

@@ -140,7 +140,7 @@ pygments_style = 'trac'
 # branch, which is located at this URL.
 intersphinx_mapping = {
     'python': ('https://docs.python.org/3/', None),
-    'sphinx': ('http://www.sphinx-doc.org/en/master/', None),
+    'sphinx': ('https://www.sphinx-doc.org/en/master/', None),
     'psycopg2': ('http://initd.org/psycopg/docs/', None),
 }
 

docs/internals/contributing/writing-documentation.txt

@@ -42,7 +42,7 @@ Django's documentation uses the Sphinx__ documentation system, which in turn
 is based on docutils__. The basic idea is that lightly-formatted plain-text
 documentation is transformed into HTML, PDF, and any other output format.
 
-__ http://sphinx-doc.org/
+__ https://www.sphinx-doc.org/
 __ http://docutils.sourceforge.net/
 
 To build the documentation locally, install Sphinx:

docs/intro/whatsnext.txt

@@ -183,7 +183,7 @@ You can get a local copy of the HTML documentation following a few steps:
 
 * The HTML documentation will be placed in ``docs/_build/html``.
 
-__ http://sphinx-doc.org/
+__ https://www.sphinx-doc.org/
 __ https://www.gnu.org/software/make/
 
 .. _differences-between-doc-versions: