Remove unnecessary const_cast

Former-commit-id: 724dc8226e

src/Kyoto/CToken.cpp

@@ -54,7 +54,7 @@ void CToken::Unlock() {
 }
 
 CToken& CToken::operator=(const CToken& other) {
-  if (&other == const_cast< const CToken* >(this)) {
+  if (&other == this) {
     return *this;
   }