Revert "gsk: Change the default renderer"

This reverts commit 98e3fca284.

We got sufficient testing to determine that the new renderers
need more time to mature.

As somebody said, "this shit is hard."

gsk/gskrenderer.c

@@ -632,7 +632,7 @@ get_renderer_for_backend (GdkSurface *surface)
 static GType
 get_renderer_for_gl (GdkSurface *surface)
 {
-  return gsk_ngl_renderer_get_type ();
+  return GSK_TYPE_GL_RENDERER;
 }
 
 static GType
@@ -645,12 +645,6 @@ get_renderer_for_vulkan (GdkSurface *surface)
 #endif
 }
 
-static GType
-get_renderer_for_gles2 (GdkSurface *surface)
-{
-  return GSK_TYPE_GL_RENDERER;
-}
-
 static GType
 get_renderer_fallback (GdkSurface *surface)
 {
@@ -664,7 +658,6 @@ static struct {
   { get_renderer_for_env_var },
   { get_renderer_for_backend },
   { get_renderer_for_gl },
-  { get_renderer_for_gles2 },
   { get_renderer_for_vulkan },
   { get_renderer_fallback },
 };