build: Fix include names for mutter->muffin.

I was wrong:
linuxmint/muffin#726 (comment)

Author: mtwebster

src/cinnamon-global.c

@@ -7,7 +7,7 @@
 #include "cinnamon-global-private.h"
 #include "cinnamon-screen.h"
 #include <meta/meta-x11-display.h>
-#include <meta/compositor-mutter.h>
+#include <meta/compositor-muffin.h>
 #include <meta/meta-cursor-tracker.h>
 #include <meta/meta-background-actor.h>
 #include <meta/meta-settings.h>

src/cinnamon-recorder.c

@@ -16,7 +16,7 @@
 #include <cogl/cogl.h>
 #include <meta/meta-cursor-tracker.h>
 #include <meta/display.h>
-#include <meta/compositor-mutter.h>
+#include <meta/compositor-muffin.h>
 #include <st/st.h>
 
 #include "cinnamon-global.h"

src/cinnamon-screen.c

@@ -29,7 +29,7 @@
 #include <meta/meta-backend.h>
 #include <meta/meta-enum-types.h>
 #include <meta/meta-cursor-tracker.h>
-#include <meta/compositor-mutter.h>
+#include <meta/compositor-muffin.h>
 #include <meta/meta-monitor-manager.h>
 #include <meta/window.h>