Update backtracking/subarray_sum.cpp

Co-authored-by: David Leal <halfpacho@gmail.com>

Author: Swastyy

backtracking/subarray_sum.cpp

@@ -60,7 +60,7 @@ std::uint64_t subarray_sum(int sum, const std::vector<int> &in_arr) {
 }  // namespace backtracking
 
 /**
- * @brief Test implementations
+ * @brief Self-test implementations
  * @returns void
  */
 static void test() {