Bug 1371564 - Bustage fix, correct flag name in assertion. no_r=me

layout/generic/nsTextFrame.cpp

@@ -1121,7 +1121,7 @@ public:
     }
 
     void Finish(gfxMissingFontRecorder* aMFR) {
-      MOZ_ASSERT(!(mTextRun->GetFlags2() & nsTextFrameUtils::Flags::TEXT_UNUSED_FLAG),
+      MOZ_ASSERT(!(mTextRun->GetFlags2() & nsTextFrameUtils::Flags::TEXT_UNUSED_FLAGS),
                    "Flag set that should never be set! (memory safety error?)");
       if (mTextRun->GetFlags2() & nsTextFrameUtils::Flags::TEXT_IS_TRANSFORMED) {
         nsTransformedTextRun* transformedTextRun =