Clean up layout-files

- Change text to symbols
- Remove unused button-definitions

This makes these layout-files easier to understand and edit.

Part-of: <https://gitlab.gnome.org/World/Phosh/squeekboard/-/merge_requests/629>

data/keyboards/ch+fr.yaml

@@ -80,5 +80,3 @@ buttons:
         outline: "wide"
         icon: "key-enter"
         keysym: "Return"
-    "\"":
-        keysym: "quotedbl"