[libc++][NFC] Enable modernize-use-override

Reviewed By: Mordante, #libc

Spies: aheejin, libcxx-commits, smeenai

Differential Revision: https://reviews.llvm.org/D124714

NOKEYCHECK=True
GitOrigin-RevId: 4262b523ff16928ff6edfb303081bf470b99cac2
diff --git a/include/exception b/include/exception
index 6b164e1..04057c3 100644
--- a/include/exception
+++ b/include/exception
@@ -156,8 +156,8 @@
 class _LIBCPP_EXCEPTION_ABI bad_exception : public exception {
 public:
   _LIBCPP_INLINE_VISIBILITY bad_exception() _NOEXCEPT {}
-  virtual ~bad_exception() _NOEXCEPT;
-  virtual const char* what() const _NOEXCEPT;
+  ~bad_exception() _NOEXCEPT override;
+  const char* what() const _NOEXCEPT override;
 };
 #endif // !_LIBCPP_ABI_VCRUNTIME