[clang-tidy] Make deleted member functions public

Making them private was a way to hide them, we can explicitly delete
them, which give a better compilation error message as well.

Also see: https://stackoverflow.com/q/55205874

Bug: v8:10488
Change-Id: Ieffa05951aeefc0225f8fb84e756eb67353e57a3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2211184Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67982}

src/torque/types.h

@@ -104,6 +104,7 @@ struct RuntimeType {
 
 class V8_EXPORT_PRIVATE Type : public TypeBase {
  public:
+  Type& operator=(const Type& other) = delete;
   virtual bool IsSubtypeOf(const Type* supertype) const;
 
   // Default rendering for error messages etc.
@@ -164,7 +165,6 @@ class V8_EXPORT_PRIVATE Type : public TypeBase {
   Type(TypeBase::Kind kind, const Type* parent,
        MaybeSpecializationKey specialized_from = base::nullopt);
   Type(const Type& other) V8_NOEXCEPT;
-  Type& operator=(const Type& other) = delete;
   void set_parent(const Type* t) { parent_ = t; }
   int Depth() const;
   virtual std::string ToExplicitString() const = 0;