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/x86/jni_macro_assembler_x86.cc b/compiler/utils/x86/jni_macro_assembler_x86.cc
index df946bd..540d72b 100644
--- a/compiler/utils/x86/jni_macro_assembler_x86.cc
+++ b/compiler/utils/x86/jni_macro_assembler_x86.cc
@@ -28,7 +28,7 @@
 class X86ExceptionSlowPath final : public SlowPath {
  public:
   explicit X86ExceptionSlowPath(size_t stack_adjust) : stack_adjust_(stack_adjust) {}
-  virtual void Emit(Assembler *sp_asm) override;
+  void Emit(Assembler *sp_asm) override;
  private:
   const size_t stack_adjust_;
 };