Wrong namespace in deprecation message drupal_set_time_limit()

This is a follow up issue on #3000057: Deprecate drupal_set_time_limit() and file_upload_max_size() and move to Environment component and its change record.

Problem/Motivation

It seems that the 8.7.x and onwards have the deprecation warning for drupal_set_time_limit() wrong and suggests it as per the below:

 * @deprecated in Drupal 8.7.0 and will be removed before Drupal 9.0.0. Use
 *   \Drupal\Core\Environment::setTimeLimit() instead.
 *
 * @see https://www.drupal.org/node/3000058
 */
function drupal_set_time_limit($time_limit) {
  @trigger_error('drupal_set_time_limit() is deprecated in Drupal 8.7.0 and will be removed before Drupal 9.0.0. Use \Drupal\Core\Environment::setTimeLimit() instead. See https://www.drupal.org/node/3000058.', E_USER_DEPRECATED);
  Environment::setTimeLimit($time_limit);
}

Proposed resolution

The other procedural functionfile_upload_max_size() seems like it has been updated with the correct namespace, but drupal_set_time_limit() still needs to point to namespace Drupal\Component\Utility\Environment for both the annotation and @trigger_error message.

Remaining tasks

Review & test.

User interface changes

None.

API changes

None.

Data model changes

None.