Bug 1265275 Removed using namespace mozilla; and using namespace mozilla::dom; from PresentationAvailability.cpp r=smaug

Depends on D81855

Differential Revision: https://phabricator.services.mozilla.com/D81948

dom/presentation/PresentationAvailability.cpp

@@ -15,8 +15,6 @@
 #include "nsServiceManagerUtils.h"
 #include "PresentationLog.h"
 
-using namespace mozilla;
-using namespace mozilla::dom;
 namespace mozilla {
 namespace dom {