Fix c++ style comment

programs/zstdcli.c

@@ -1307,7 +1307,7 @@ int main(int argCount, const char* argv[])
             DISPLAYLEVEL(3, "Note: %d physical core(s) detected \n", nbWorkers);
         }
     }
-    // Resolve to default if nbWorkers is still unset
+    /* Resolve to default if nbWorkers is still unset */
     if (nbWorkers == -1) {
       if (operation == zom_decompress) {
         nbWorkers = 1;