Fix docs build by pinning indirect dependencies

docs/requirements.txt

@@ -8,7 +8,14 @@
 #
 dask-sphinx-theme>=3.0.5
 myst-parser
-sphinx
+
+# FIXME: Cleanup this workaround to the issue described in
+#        https://github.com/dask/dask-sphinx-theme/issues/68#issuecomment-1893198477
+#        when its possible.
+sphinxcontrib-applehelp<1.0.5
+sphinxcontrib-devhelp<1.0.6
+sphinxcontrib-htmlhelp<2.0.5
+sphinxcontrib-serializinghtml<1.1.10
 
 # sphinx-autobuild enables the "make devenv" command defined in the Makefile to
 # automatically rebuild the documentation on changes and update live-reload a