Remove superfluous 'virtual' specifiers in ART.

Remove 'virtual' specifier on methods already bearing the 'override'
specifier.

Test: mmma art
Change-Id: I114930969a5ca048d88de9ecd18e2c6403593e31
diff --git a/compiler/utils/jni_macro_assembler.h b/compiler/utils/jni_macro_assembler.h
index e0c2992..e6130cf 100644
--- a/compiler/utils/jni_macro_assembler.h
+++ b/compiler/utils/jni_macro_assembler.h
@@ -299,7 +299,7 @@
   JNIMacroLabelCommon() : JNIMacroLabel(kIsa) {
   }
 
-  virtual ~JNIMacroLabelCommon() override {}
+  ~JNIMacroLabelCommon() override {}
 
  private:
   PlatformLabel label_;