message: fix(ci): pin mtools version to python3.6-compatible one
diff: @@ -122,7 +122,9 @@ export async function getMlaunchPath(): Promise<{ exec: string[], env: Record<st
  ciLog('Trying to install mlaunch in ', tmpdir);
  // Pin pymongo to 3.12.2 because mlaunch does not seem to be compatible
  // with 4.0, see https://jira.mongodb.org/browse/MONGOSH-1072
  - await execFile('pip3', ['install', '--target', tmpdir, 'mtools[mlaunch]', 'pymongo==3.12.2']);
  + // Also pin mlaunch to 1.6.4, since we have Python 3.6 in CI and 1.7.0
  + // drops Python 3.6 support.
  + await execFile('pip3', ['install', '--target', tmpdir, 'mtools[mlaunch]==1.6.4', 'pymongo==3.12.2']);
  ciLog('Installation complete');
  [ exec ] = await tryExtensions(mlaunchPy);
  if (exec) {
  