chore(deps): update squidfunk/mkdocs-material docker tag to v8.3.4

a bit pedantic but ok

Dockerfile

@@ -1,4 +1,4 @@
-FROM squidfunk/mkdocs-material:8.3.3
+FROM squidfunk/mkdocs-material:8.3.4
 
 EXPOSE 8000
 

docs/index.md

@@ -18,7 +18,7 @@ We'd be happy to hear feedback about our documentation, if it was helpful, what
 
     This project is still [beta quality software](https://en.wikipedia.org/wiki/Software_release_life_cycle#Beta) :bomb: Please take that into consideration if you are thinking about using this system in production. We're working hard to make Co-op Cloud stable. In the meantime, this is a good time to help us out with initial testing, feedback, ideas or [join in with development](/get-involved/).
 
-- [Operators guide](/operators/): You run a Co-op Cloud deployment or want to do so :computer:
+- [Operators guide](/operators/): You run a Co-op Cloud based deployment or want to do so :computer:
 
 - [Maintainers guide](/maintainers/): You maintain recipes and ensure things run smoothly for operators :tools:
 

docs/operators/tutorial.md

@@ -109,7 +109,7 @@ You need to keep port `:80` and `:443` free on your server for web proxying to y
 wget -O- https://get.docker.com | bash
 
 # add user to docker group
-usermod -aG docker $USER
+sudo usermod -aG docker $USER
 
 # setup swarm
 docker swarm init