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/libdexfile/dex/art_dex_file_loader.cc b/libdexfile/dex/art_dex_file_loader.cc
index f50bf1c..eb7d3d3 100644
--- a/libdexfile/dex/art_dex_file_loader.cc
+++ b/libdexfile/dex/art_dex_file_loader.cc
@@ -40,7 +40,7 @@
 class MemMapContainer : public DexFileContainer {
  public:
   explicit MemMapContainer(MemMap&& mem_map) : mem_map_(std::move(mem_map)) { }
-  virtual ~MemMapContainer() override { }
+  ~MemMapContainer() override { }
 
   int GetPermissions() override {
     if (!mem_map_.IsValid()) {