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/pl.yaml

@@ -20,13 +20,13 @@ views:
     numbers:
         - "1 2 3 4 5 6 7 8 9 0"
         - "@ # $ % & - _ + ( )"
-        - "show_symbols   , \" ' colon ; ! ?  BackSpace"
-        - "show_letters preferences         space        period Return"
+        - "show_symbols   , \" ' : ; ! ?  BackSpace"
+        - "show_letters preferences         space        . Return"
     symbols:
         - "~ ` | · √ π τ ÷ × ¶"
         - "© ® £ € ¥ ^ ° * { }"
         - "show_numbers_from_symbols   \\ / < > = [ ]  BackSpace"
-        - "show_letters preferences         space        period Return"
+        - "show_letters preferences         space        . Return"
     accents:
         - "q w ę r t y u i ó p"
         - "ą ś d f g h j k ł"
@@ -100,9 +100,8 @@ buttons:
                     - "accents"
         outline: "altline"
         label: "ĄĘ"
-    period:
+    .:
         outline: "altline"
-        text: "."
     space:
         outline: "spaceline"
         text: " "
@@ -110,5 +109,3 @@ buttons:
         outline: "wide"
         icon: "key-enter"
         keysym: "Return"
-    colon:
-        text: ":"