[gtk/bilelmoussaoui/gsk-docs] docs: sync up renderer flags

[Bilal Elmoussaoui <bilelmoussaoui src gnome org>]

commit 49e678e0d2d83349215b449f0253cefbd9cbe543
Author: Bilal Elmoussaoui <bil elmoussaoui gmail com>
Date:   Thu Jan 6 20:00:41 2022 +0000

    docs: sync up renderer flags

 docs/reference/gtk/running.md | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)
---
diff --git a/docs/reference/gtk/running.md b/docs/reference/gtk/running.md
index 924c5b344f..b6a6cd0034 100644
--- a/docs/reference/gtk/running.md
+++ b/docs/reference/gtk/running.md
@@ -330,14 +330,8 @@ using and the GDK backend supports them:
 `cairo`
 : Selects the fallback Cairo renderer
 
-`opengl`
-: Selects the default OpenGL renderer
-
 `gl`
-: Selects the "gl" OpenGL renderer
-
-`ngl`
-: Selects the "ngl" OpenGL renderer
+: Selects the OpenGL renderer
 
 `vulkan`
 : Selects the Vulkan renderer