Update comments in config

mautrix_signal/example-config.yaml

@@ -41,7 +41,6 @@ appservice:
     max_body_size: 1
 
     # The full URI to the database. SQLite and Postgres are supported.
-    # However, SQLite support is extremely experimental and should not be used.
     # Format examples:
     #   SQLite:   sqlite:///filename.db
     #   Postgres: postgres://username:password@hostname/dbname
@@ -115,7 +114,7 @@ signal:
 # Bridge config
 bridge:
     # Localpart template of MXIDs for Signal users.
-    # {userid} is replaced with an identifier for the Signal user.
+    # {userid} is replaced with the UUID of the Signal user.
     username_template: "signal_{userid}"
     # Displayname template for Signal users.
     # {displayname} is replaced with the displayname of the Signal user, which is the first