Modernise code to use override specifier

Generated by clang-tidy, with IgnoreDestructors option enabled.

Test: m checkbuild
Bug: 116509795
Change-Id: I5dafa10c2cf605165581b8cf7dd2633ed101ed65
diff --git a/compiler/optimizing/codegen_test_utils.h b/compiler/optimizing/codegen_test_utils.h
index 0289e9c..dde39d4 100644
--- a/compiler/optimizing/codegen_test_utils.h
+++ b/compiler/optimizing/codegen_test_utils.h
@@ -176,7 +176,7 @@
  public:
   InternalCodeAllocator() : size_(0) { }
 
-  virtual uint8_t* Allocate(size_t size) {
+  uint8_t* Allocate(size_t size) override {
     size_ = size;
     memory_.reset(new uint8_t[size]);
     return memory_.get();