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/cz+qwerty_wide.yaml

@@ -20,7 +20,7 @@ views:
     numbers:
         - "1 2 3 4 5 6 7 8 9 0"
         - "@ # $ % & - _ + ( )"
-        - "show_symbols    , \" ' colon ; ! ?    BackSpace"
+        - "show_symbols    , \" ' : ; ! ?    BackSpace"
         - "show_letters preferences show_accents    space    , . Return"
     symbols:
         - "~ ` | · √ π τ ÷ × ¶"
@@ -102,5 +102,3 @@ buttons:
         outline: "wide"
         icon: "key-enter"
         keysym: "Return"
-    colon:
-        text: ":"