Bump sphinx from 3.5.1 to 3.5.2 in /requirements (#16683)

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 3.5.1 to 3.5.2.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/3.x/CHANGES)
- [Commits](https://github.com/sphinx-doc/sphinx/compare/v3.5.1...v3.5.2)

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

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

requirements/docs.txt

@@ -9,9 +9,9 @@ Pygments==2.8.0 \
     --hash=sha256:b21b072d0ccdf29297a82a2363359d99623597b8a265b8081760e4d0f7153c88 \
     --hash=sha256:37a13ba168a02ac54cc5891a42b1caec333e59b66addb7fa633ea8a6d73445c0
 # Sphinx is required by sphinxcontrib-httpdomain
-Sphinx==3.5.1 \
-    --hash=sha256:e90161222e4d80ce5fc811ace7c6787a226b4f5951545f7f42acf97277bfc35c \
-    --hash=sha256:11d521e787d9372c289472513d807277caafb1684b33eb4f08f7574c405893a9
+Sphinx==3.5.2 \
+    --hash=sha256:ef64a814576f46ec7de06adf11b433a0d6049be007fefe7fd0d183d28b581fac \
+    --hash=sha256:672cfcc24b6b69235c97c750cb190a44ecd72696b4452acaf75c2d9cc78ca5ff
 # alabaster is required by Sphinx
 alabaster==0.7.12 \
     --hash=sha256:446438bdcca0e05bd45ea2de1668c1d9b032e1a9154c2c259092d77031ddd359 \