[gtk/matthiasc/for-main] docs; Update supported backends

[Matthias Clasen <matthiasc src gnome org>]

commit fb5b2d3d8eded8d9dc25df5483d33868db6d47f0
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Jan 6 14:56:16 2022 -0500

    docs; Update supported backends
    
    Some strings have changed here.

 docs/reference/gtk/running.md | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)
---
diff --git a/docs/reference/gtk/running.md b/docs/reference/gtk/running.md
index 924c5b344f..722c320256 100644
--- a/docs/reference/gtk/running.md
+++ b/docs/reference/gtk/running.md
@@ -286,7 +286,7 @@ requires that GTK is compiled with support for that backend.
 The following backends can be selected, provided they are
 included in the GDK libraries you are using:
 
-`quartz`
+`macos`
 : Selects the native Quartz backend
 
 `win32`
@@ -336,9 +336,6 @@ using and the GDK backend supports them:
 `gl`
 : Selects the "gl" OpenGL renderer
 
-`ngl`
-: Selects the "ngl" OpenGL renderer
-
 `vulkan`
 : Selects the Vulkan renderer