Fix missing Attribute dtor in GCC 11.

Parser bindings are expecting this, yet this was optimized out under GCC
11.

src/CppParser/AST.cpp

@@ -1078,6 +1078,8 @@ HTMLStartTagComment::Attribute::Attribute() {}
 
 HTMLStartTagComment::Attribute::Attribute(const Attribute& rhs) : name(rhs.name), value(rhs.value) {}
 
+HTMLStartTagComment::Attribute::~Attribute() {}
+
 HTMLStartTagComment::HTMLStartTagComment() : HTMLTagComment(CommentKind::HTMLStartTagComment) {}
 
 DEF_VECTOR(HTMLStartTagComment, HTMLStartTagComment::Attribute, Attributes)

src/CppParser/AST.h

@@ -201,6 +201,7 @@ public:
     public:
         Attribute();
         Attribute(const Attribute&);
+        ~Attribute();
         std::string name;
         std::string value;
     };