Update docker.io/library/postgres Docker tag to v13

docs/guides/matrix-create-room.md

@@ -11,7 +11,7 @@ title: "Matrix: Create a New Room"
 ## 1. Create the Room
 
 Rooms are always created by the *CCCHH-Admin* Account whose credentials can be found in *infra-secrets*.
-To create a room, log in to [https://element.hamburg.ccc.de](https://element.hamburg.ccc.de) and click on *New Conversation* -> *New Room*.
+To create a room, log in to https://element.hamburg.ccc.de and click on *New Conversation* -> *New Room*.
 Enter a Room Name and optionally give it an address on the *hamburg.ccc.de* server.
 
 ## 2. Configure Room Metadata