Fixed Travis Build

Somehow travis cannot build the docs automatically due to a configuration error. Maybe this fixes the error.

https://squidfunk.github.io/mkdocs-material/extensions/codehilite/#adding-line-numbers

mkdocs.yml

@@ -7,11 +7,14 @@ edit_uri: ../mailcow-dockerized-docs/edit/master/docs/
 remote_branch: gh-pages
 theme: material
 markdown_extensions:
-  - codehilite(guess_lang=true)
-  - toc(permalink=true)
+  - codehilite
+      guess_lang: true
+  - toc
+      permalink: true
   - admonition
   - pymdownx.magiclink
-  - pymdownx.tasklist(custom_checkbox=true)
+  - pymdownx.tasklist
+      custom_checkbox: true
   - pymdownx.mark
   - pymdownx.tilde
   - pymdownx.extra