Fixed Github Actions workflow

Author: squidfunk

.github/workflows/documentation.yml

@@ -60,6 +60,7 @@ jobs:
             "mkdocs-git-committers-plugin-2<1" \
             "mkdocs-git-revision-date-localized-plugin>=1.0" \
             "mkdocs-minify-plugin>=0.3" \
+            "mkdocs-rss-plugin>=1.1.0" \
             "mkdocs-redirects>=1.0"
 
       - name: Install Insiders build