Remove unnecessary functions

apiOptionsSet not required in bg/js/api.js after optionsSave; optionsSave already invokes apiOptionsSet.
apiOptionsSet not required in fg/js/api.js since it's never invoked by the foreground.
optionsSet handler not required in bg/js/backend.js since the message is never sent by the foreground.

ext/bg/js/api.js

@@ -138,7 +138,6 @@ async function apiCommandExec(command) {
             const options = apiOptionsGetSync();
             options.general.enable = !options.general.enable;
             await optionsSave(options);
-            await apiOptionsSet(options);
         }
     };
 

ext/bg/js/backend.js

@@ -85,10 +85,6 @@ class Backend {
                 forward(apiOptionsGet(), callback);
             },
 
-            optionsSet: ({options, callback}) => {
-                forward(apiOptionsSet(options), callback);
-            },
-
             kanjiFind: ({text, callback}) => {
                 forward(apiKanjiFind(text), callback);
             },

ext/fg/js/api.js

@@ -17,10 +17,6 @@
  */
 
 
-function apiOptionsSet(options) {
-    return utilInvoke('optionsSet', {options});
-}
-
 function apiOptionsGet() {
     return utilInvoke('optionsGet');
 }