cleanup: Use consistent 4-space indent

This is another bit where we've made good progress, and just need
a final push to complete the transition.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2866>

js/misc/inputMethod.js

@@ -42,7 +42,7 @@ export const InputMethod = GObject.registerClass({
 
         this._inputSourceManager = Keyboard.getInputSourceManager();
         this._sourceChangedId = this._inputSourceManager.connect('current-source-changed',
-                                                                 this._onSourceChanged.bind(this));
+            this._onSourceChanged.bind(this));
         this._currentSource = this._inputSourceManager.currentSource;
 
         if (this._ibus.is_connected())