[mutter] cogl: Update documentation for COGL_PRIVATE_FEATURE_ANY_GL

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit e32e20521dccc14b83b4f533a1c986efc23d9db2
Author: Adam Jackson <ajax redhat com>
Date:   Wed Oct 23 12:08:47 2019 -0400

    cogl: Update documentation for COGL_PRIVATE_FEATURE_ANY_GL
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/973

 cogl/cogl/cogl-private.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/cogl/cogl/cogl-private.h b/cogl/cogl/cogl-private.h
index 5a96d6d42..e13300920 100644
--- a/cogl/cogl/cogl-private.h
+++ b/cogl/cogl/cogl-private.h
@@ -64,9 +64,9 @@ typedef enum
    * is first allocated or when it is shown or resized */
   COGL_PRIVATE_FEATURE_DIRTY_EVENTS,
   COGL_PRIVATE_FEATURE_ENABLE_PROGRAM_POINT_SIZE,
-  /* These features let us avoid conditioning code based on the exact
-   * driver being used and instead check for broad opengl feature
-   * sets that can be shared by several GL apis */
+  /* This feature allows for explicitly selecting a GL-based backend,
+   * as opposed to nop or (in the future) Vulkan.
+   */
   COGL_PRIVATE_FEATURE_ANY_GL,
 
   COGL_N_PRIVATE_FEATURES