Do not use async exec in setupTaskcluster.js

scripts/setupTaskcluster.js

@@ -3,10 +3,6 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 import * as exec from "child_process";
-import { promisify } from "util";
-
-// Define an async/await version of "exec".
-const execAsync = promisify(exec.exec);
 
 // If this is not running on TaskCluster, exit
 // without an error code.
@@ -18,5 +14,5 @@ if ('TASK_ID' in process.env) {
   // be installed. That package is required for Glean to build.
   // We make sure to have all the dependencies in place when on
   // TaskCluster by running the commands manually.
-  execAsync("sudo apt-get -y install python3-venv");
+  exec.exec("sudo apt-get -y install python3-venv");
 }