docs: replace electron.atom.io with electronjs.org in docs/fiddles (#22196)

docs/fiddles/menus/customize-menus/index.html

@@ -21,7 +21,7 @@
 
       <p>
         Open the
-        <a href="http://electron.atom.io/docs/api/menu"
+        <a href="https://electronjs.org/docs/api/menu"
           >full API documentation<span
             >(opens in new window)</span
           ></a
@@ -111,7 +111,7 @@
           <p>
             See the full
             <a
-              href="http://electron.atom.io/docs/api/web-contents/#event-context-menu"
+              href="https://electronjs.org/docs/api/web-contents/#event-context-menu"
               >context-menu event documentation</a
             >
             for all the available properties.

docs/fiddles/menus/customize-menus/main.js

@@ -159,7 +159,7 @@ const template = [
       {
         label: 'Learn More',
         click: () => {
-          shell.openExternal('http://electron.atom.io')
+          shell.openExternal('https://electronjs.org')
         }
       }
     ]