apps-menu: Use stylesheet to set width

The `style` property is useful for computed CSS declarations,
but for regular styling the stylesheet is preferable.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell-extensions/-/merge_requests/290>

extensions/apps-menu/extension.js

@@ -590,7 +590,6 @@ class ApplicationsButton extends PanelMenu.Button {
 
     _display() {
         this._applicationsButtons.clear();
-        this.mainBox.style = 'width: 35em;';
         this.mainBox.hide();
 
         // Load categories

extensions/apps-menu/stylesheet.css

@@ -4,6 +4,8 @@
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
+.apps-menu {width: 26em;}
+
 .apps-menu:ltr {
     padding-right: 3px;
 }