Bump sphinx from 3.5.4 to 4.0.1 in /requirements (#17115)

* Bump sphinx from 3.5.4 to 4.0.1 in /requirements

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 3.5.4 to 4.0.1.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/4.x/CHANGES)
- [Commits](https://github.com/sphinx-doc/sphinx/compare/v3.5.4...v4.0.1)

Signed-off-by: dependabot[bot] <support@github.com>

* upgrade docutils to 0.17.1 at the same time

* Update index.rst

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Andrew Williamson <awilliamson@mozilla.com>

docs/topics/development/index.rst

@@ -18,7 +18,6 @@ Development
    logging
    services
    translations
-   style
    search
    docs
    ../../../README.rst

requirements/docs.txt

@@ -9,9 +9,9 @@ Pygments==2.10.0 \
     --hash=sha256:b8e67fe6af78f492b3c4b3e2970c0624cbf08beb1e493b2c99b9fa1b67a20380 \
     --hash=sha256:f398865f7eb6874156579fdf36bc840a03cab64d1cde9e93d68f46a425ec52c6
 # Sphinx is required by sphinxcontrib-httpdomain
-Sphinx==3.5.4 \
-    --hash=sha256:2320d4e994a191f4b4be27da514e46b3d6b420f2ff895d064f52415d342461e8 \
-    --hash=sha256:19010b7b9fa0dc7756a6e105b2aacd3a80f798af3c25c273be64d7beeb482cb1
+Sphinx==4.0.1 \
+    --hash=sha256:b2566f5f339737a6ef37198c47d56de1f4a746c722bebdb2fe045c34bfd8b9d0 \
+    --hash=sha256:cf5104777571b2b7f06fa88ee08fade24563f4a0594cf4bd17d31c47b8740b4c
 # alabaster is required by Sphinx
 alabaster==0.7.12 \
     --hash=sha256:446438bdcca0e05bd45ea2de1668c1d9b032e1a9154c2c259092d77031ddd359 \
@@ -21,9 +21,9 @@ Babel==2.9.1 \
     --hash=sha256:ab49e12b91d937cd11f0b67cb259a57ab4ad2b59ac7a3b41d6c06c0ac5b0def9 \
     --hash=sha256:bc0c176f9f6a994582230df350aa6e05ba2ebe4b3ac317eab29d9be5d2768da0
 # docutils is required by Sphinx
-docutils==0.16 \
-    --hash=sha256:0c5b78adfbf7762415433f5515cd5c9e762339e23369dbe8000d84a4bf4ab3af \
-    --hash=sha256:c2de3a60e9e7d07be26b7f2b00ca0309c207e06c100f9cc2a94931fc75a478fc
+docutils==0.17.1 \
+    --hash=sha256:cf316c8370a737a022b72b56874f6602acf974a37a9fba42ec2876387549fc61 \
+    --hash=sha256:686577d2e4c32380bb50cbb22f575ed742d58168cee37e99117a854bcd88f125
 # imagesize is required by Sphinx
 imagesize==1.2.0 \
     --hash=sha256:6965f19a6a2039c7d48bca7dba2473069ff854c36ae6f19d2cde309d998228a1 \