Merge pull request #7778 from andreasabel/sphinx-req-7777

Fix #7777: upgrade requirements.txt to latest versions

doc/requirements.in

+sphinx >= 3.1
+sphinx_rtd_theme
+sphinx-jsonschema

doc/requirements.txt

-sphinx == 3.1.*
-sphinx_rtd_theme
-sphinx-jsonschema == 1.16.*
+#
+# This file is autogenerated by pip-compile with python 3.9
+# To update, run:
+#
+#    pip-compile requirements.in
+#
+alabaster==0.7.12
+    # via sphinx
+babel==2.9.1
+    # via sphinx
+certifi==2021.10.8
+    # via requests
+charset-normalizer==2.0.7
+    # via requests
+docutils==0.17.1
+    # via
+    #   sphinx
+    #   sphinx-jsonschema
+    #   sphinx-rtd-theme
+idna==2.10
+    # via requests
+imagesize==1.2.0
+    # via sphinx
+jinja2==2.11.3
+    # via sphinx
+jsonpointer==2.1
+    # via sphinx-jsonschema
+markupsafe==1.1.1
+    # via jinja2
+packaging==20.9
+    # via sphinx
+pygments==2.5.2
+    # via sphinx
+pyparsing==2.4.7
+    # via packaging
+pytz==2021.3
+    # via babel
+pyyaml==5.4.1
+    # via sphinx-jsonschema
+requests==2.26.0
+    # via
+    #   sphinx
+    #   sphinx-jsonschema
+snowballstemmer==2.1.0
+    # via sphinx
+sphinx==4.2.0
+    # via
+    #   -r requirements.in
+    #   sphinx-rtd-theme
+sphinx-jsonschema==1.16.11
+    # via -r requirements.in
+sphinx-rtd-theme==1.0.0
+    # via -r requirements.in
+sphinxcontrib-applehelp==1.0.2
+    # via sphinx
+sphinxcontrib-devhelp==1.0.2
+    # via sphinx
+sphinxcontrib-htmlhelp==2.0.0
+    # via sphinx
+sphinxcontrib-jsmath==1.0.1
+    # via sphinx
+sphinxcontrib-qthelp==1.0.3
+    # via sphinx
+sphinxcontrib-serializinghtml==1.1.5
+    # via sphinx
+urllib3==1.26.7
+    # via requests
+
+# The following packages are considered to be unsafe in a requirements file:
+# setuptools