Replace MailFormatHelper::htmlToMailUrls() with a self-contained method used from MailFormatHelper::htmlToText() in the same way it uses MailFormatHelper::htmlToTextPad()

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Fixed failed commands on #28
Attached patch against Drupal 10.1.x
Attached reroll patch

+    @trigger_error('MailFormatHelper::htmlToMailUrls() is deprecated in Drupal 8.5.0 and will be removed before Drupal 9.0.0. Instead, you should use \Drupal\Core\Mail\MailFormatHelper::htmlToTextUrls(). See https://www.drupal.org/node/2932899.', E_USER_DEPRECATED);

The deprecation message should mention Drupal 10 and Drupal 11, as the added comments do, for example the following one.

+   * @deprecated in drupal:10.1.0 and is removed from drupal:11.0.0. Instead, use
+   *   \Drupal\Core\Mail\MailFormatHelper::htmlToTextUrls().

The last patch fixed what I reported in my previous comment. Let's see if the tests pass.