Bug 1757576 - Fix non-unified-build bustage in dom/media/gmp/GMPParent.cpp; r=media-playback-reviewers,bryce

Differential Revision: https://phabricator.services.mozilla.com/D139948

dom/media/gmp/GMPParent.cpp

@@ -23,6 +23,7 @@
 #endif
 #include "mozilla/Services.h"
 #include "mozilla/SSE.h"
+#include "mozilla/StaticPrefs_media.h"
 #include "mozilla/SyncRunnable.h"
 #include "mozilla/Telemetry.h"
 #include "mozilla/Unused.h"