[mutter] readme: Fix typo

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

commit b9fc7416605ad071ff427ea9a76433f40be6755c
Author: Julia Johannesen <julia insertdomain name>
Date:   Fri Jul 29 19:18:13 2022 +0000

    readme: Fix typo
    
    "af" -> "of"
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2542>

 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/README.md b/README.md
index 163918c02f..fa39646c98 100644
--- a/README.md
+++ b/README.md
@@ -14,7 +14,7 @@ window compositing, focus tracking, workspace management, keybindings and
 monitor configuration.
 
 Internally it uses a fork of Cogl, a hardware acceleration abstraction library
-used to simplify usage of OpenGL pipelines, as well as a fork af Clutter, a
+used to simplify usage of OpenGL pipelines, as well as a fork of Clutter, a
 scene graph and user interface toolkit.
 
 Mutter is used by, for example, GNOME Shell, the GNOME core user interface, and