crypto: fix memory leak in CipherBase::Final

fix #7497

Signed-off-by: Fedor Indutny <fedor@indutny.com>

src/node_crypto.cc

@@ -2846,6 +2846,7 @@ void CipherBase::Final(const FunctionCallbackInfo<Value>& args) {
 
   args.GetReturnValue().Set(
       Buffer::New(env, reinterpret_cast<char*>(out_value), out_len));
+  delete[] out_value;
 }