restore mkdocs-redirects to requirements.in

Author: marionbarker

requirements.in

@@ -7,3 +7,4 @@ mkdocs-include-markdown-plugin~=7.1.5
 mkdocs-open-in-new-tab~=1.0
 mkdocs-macros-plugin~=1.3
 mkdocs-unused-files~=0.2
+mkdocs-redirects~=1.2