layouts: Fill some placeholders with '²' and '³'

Part-of: <https://gitlab.gnome.org/World/Phosh/squeekboard/-/merge_requests/703>

data/keyboards/de+bone.yaml

@@ -22,13 +22,13 @@ views:
         - "show_upper F V Ü Ä Ö Y Z K BackSpace"
         - "show_numbers show_eschars preferences space ! ? Return"
     numbers:
-        - "1 2 3 4 5 6 7 8 9 0"
-        - "@ # € % & - _ + ( )"
+        - "1 2 3 4 5 6 7 8 9 0 ²"
+        - "@ # € % & - _ + ( ) ³"
         - "show_symbols ; \" ' : = < > BackSpace"
         - "show_letters show_eschars preferences space , . Return"
     symbols:
-        - "~ ` ´ | · √ µ ÷ × ¶"
-        - "© ® £ $ ¥ ^ ° * { }"
+        - "~ ` ´ | · √ µ ÷ × ¶ ²"
+        - "© ® £ $ ¥ ^ ° * { } ³"
         - "show_numbers \\ / § π τ [ ] BackSpace"
         - "show_letters show_eschars preferences space , . Return"
     eschars:
@@ -103,14 +103,6 @@ buttons:
     ß-subtle-highlight:
         outline: "subtle-highlight"
         text: "ß"
-    5:
-        outline: "fill"
-    "&":
-        outline: "fill"
-    ·:
-        outline: "fill"
-    ¥:
-        outline: "fill"
     ô:
         outline: "fill"
     Ç: