[clang-tidy] Use explicit default for constructor

See
https://chromium.googlesource.com/chromium/src/+/HEAD/styleguide/c++/c++-dos-and-donts.md#prefer-to-use.

Bug: v8:10488
Change-Id: I6b43374a3f5c3b0bc5a51acb0b5e0daad7d3c801
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2185969Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67655}

src/objects/string-table.h

@@ -16,7 +16,7 @@ namespace internal {
 
 class StringTableKey {
  public:
-  virtual ~StringTableKey() {}
+  virtual ~StringTableKey() = default;
   inline StringTableKey(uint32_t hash_field, int length);
 
   virtual Handle<String> AsHandle(Isolate* isolate) = 0;