Bump sphinx from 3.4.3 to 3.5.0 in /requirements (#16549)

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 3.4.3 to 3.5.0.
- [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/v3.4.3...v3.5.0)

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==3.4.3 \
-    --hash=sha256:c314c857e7cd47c856d2c5adff514ac2e6495f8b8e0f886a8a37e9305dfea0d8 \
-    --hash=sha256:41cad293f954f7d37f803d97eb184158cfd90f51195131e94875bc07cd08b93c
+Sphinx==3.5.0 \
+    --hash=sha256:68da66ca3d6b35b22bea5c53d938d5f8988663dca042f0a46429a1eba1010051 \
+    --hash=sha256:deb468efb3abaa70d790add4147d18782d86fdeacf648d6e8afb7a99807f1546
 # alabaster is required by Sphinx
 alabaster==0.7.12 \
     --hash=sha256:446438bdcca0e05bd45ea2de1668c1d9b032e1a9154c2c259092d77031ddd359 \