Bump Python requirement mkdocs-material to 8.5.7

docs-requirements.txt

 black==22.10.0
 doc8==1.0.0
 mkdocs==1.4.0
-mkdocs-material==8.5.6
+mkdocs-material==8.5.7
 mkdocstrings==0.19.0
 mkdocstrings-python==0.7.1
 recommonmark==0.7.1