[cleanup] Delete default destructor.

Bug: 
Change-Id: I597b2c1067e309c2545daef4223b3b883d15a6c1
Reviewed-on: https://chromium-review.googlesource.com/657761Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Franziska Hinkelmann <franzih@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48011}

src/debug/debug-interface.h

@@ -340,8 +340,6 @@ class V8_EXPORT_PRIVATE Coverage {
   ScriptData GetScriptData(size_t i) const;
   bool IsEmpty() const { return coverage_ == nullptr; }
 
-  ~Coverage() = default;
-
  private:
   explicit Coverage(std::shared_ptr<i::Coverage> coverage);
   std::shared_ptr<i::Coverage> coverage_;