[polari] Revert "main: Add GTK4 polyfill"

[Marge Bot <marge-bot src gnome org>]

commit 0bbd8a7334588d1097aced5e41ffc54170a45383
Author: Florian Müllner <fmuellner gnome org>
Date:   Sat Oct 10 06:08:29 2020 +0200

    Revert "main: Add GTK4 polyfill"
    
    It has done it's job now that we are on GTK4, remove it again.
    
    This reverts commit cf0854d24c0c3b9b0bf9a724184dbcc8a79c1325.
    
    Part-of: <https://gitlab.gnome.org/GNOME/polari/-/merge_requests/232>

 src/gtkShim.js  | 177 --------------------------------------------------------
 src/main.js     |   3 -
 src/meson.build |   1 -
 3 files changed, 181 deletions(-)
---
diff --git a/src/main.js b/src/main.js
index 8cda0fdb..f14d7f14 100755
--- a/src/main.js
+++ b/src/main.js
@@ -35,9 +35,6 @@ if (!pkg.checkSymbol('Soup', '3.0'))
 
 import Application from './application.js';
 
-import * as GtkShim from './gtkShim.js';
-GtkShim.init();
-
 let application = new Application();
 if (GLib.getenv('POLARI_PERSIST'))
     application.hold();
diff --git a/src/meson.build b/src/meson.build
index 24d8d454..d8ce5c42 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -12,7 +12,6 @@ js_sources = [
   'chatView.js',
   'connections.js',
   'entryArea.js',
-  'gtkShim.js',
   'initialSetup.js',
   'ircParser.js',
   'joinDialog.js',