Bump Python requirement python-gnupg to 0.5.1

docs-requirements.txt

-black==23.3.0
+black==23.7.0
 doc8==1.1.1
-mkdocs==1.4.3
-mkdocs-material==9.1.14
-mkdocstrings==0.21.2
-mkdocstrings-python==1.0.0
+mkdocs==1.5.2
+mkdocs-material==9.1.21
+mkdocstrings==0.22.0
+mkdocstrings-python==1.3.0
 recommonmark==0.7.1