remove unnecessary reference

Author: majvax

snippets/cpp/bit-manipulation/find-non-repeating-number.md

@@ -8,7 +8,7 @@ author: ashukr07
 ```cpp
 #include <vector>
 
-int find_non_repeating(const std::vector<int>& nums) {
+int find_non_repeating(const std::vector<int> nums) {
     int result = 0;
     for (const int num : nums) {
         result ^= num;