Merge branch 'bugfix/sphinx_build_failure_on_rtd_v3.1' into 'release/v3.1'

docs: Upgraded sphinx package version to prevent build failures on readthedocs…

See merge request idf/esp-idf!4555

docs/requirements.txt

@@ -1,11 +1,11 @@
 # This is a list of python packages used to generate documentation. This file is used with pip:
 # pip install -r requirements.txt
 #
-sphinx>=1.6.5
+sphinx>=1.8.4
+breathe>=4.11.1
 sphinx-rtd-theme
-breathe>=4.7.3
-sphinxcontrib.blockdiag>=1.5.3
-sphinxcontrib.seqdiag>=0.8.5
-sphinxcontrib.actdiag>=0.8.5
-sphinxcontrib.nwdiag>=0.9.5
+sphinxcontrib-blockdiag>=1.5.5
+sphinxcontrib-seqdiag>=0.8.5
+sphinxcontrib-actdiag>=0.8.5
+sphinxcontrib-nwdiag>=0.9.5
 recommonmark