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

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

data/keyboards/ch.yaml

@@ -30,8 +30,8 @@ views:
         - "show_symbols _ # & / \\ √ ; : BackSpace"
         - "show_letters show_eschars preferences space , . Return"
     symbols:
-        - "€ $ £ ¥ % | § µ [ ]"
-        - "© ® § ` { } @ · ¡ ¿"
+        - "€ $ £ ¥ % | § µ [ ] ²"
+        - "© ® § ` { } @ · ¡ ¿ ³"
         - "show_numbers « » ÷ × “ ” „ BackSpace"
         - "show_letters show_eschars preferences space , . Return"
     eschars:
@@ -87,9 +87,5 @@ buttons:
         keysym: "Return"
     °:
         outline: "fill"
-    "%":
-        outline: "fill"
-    "{":
-        outline: "fill"
     ×:
         outline: "fill"