Update to latest Sphinx version

doc/Makefile

@@ -21,6 +21,7 @@ help:
 
 # customized clean due to examples gallery
 clean:
+	rm -rf build_errors.txt
 	rm -rf $(BUILDDIR)/*
 	rm -rf $(SOURCEDIR)/examples
 	find . -type d -name "_autosummary" -exec rm -rf {} +

doc/make.bat

@@ -37,6 +37,7 @@ goto end
 rmdir /s /q %BUILDDIR% > /NUL 2>&1
 rmdir /s /q %SOURCEDIR%\examples > /NUL 2>&1
 for /d /r %SOURCEDIR% %%d in (_autosummary) do @if exist "%%d" rmdir /s /q "%%d"
+del build_errors.txt > /NUL 2>&1
 goto end
 
 :help

doc/source/conf.py

@@ -89,7 +89,7 @@
 #
 # This is also used if you do content translation via gettext catalogs.
 # Usually you set "language" from the command line for these cases.
-language = None
+language = "en"
 
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.

requirements/requirements_doc.txt

@@ -1,4 +1,4 @@
-Sphinx==4.4.0
+Sphinx==5.1.0
 jupyter_sphinx==0.4.0
 numpydoc==1.4.0
 matplotlib==3.5.1