fix memory leak

Former-commit-id: e707938902534c1694002e0ff2499cf2e0b84d9e

cpp/src/metrics/SystemInfo.cpp

@@ -245,6 +245,7 @@ SystemInfo::CPUTemperature(){
         float temp;
         fscanf(file, "%f", &temp);
         result.push_back(temp / 1000);
+        fclose(file);
     }
 
 }