Make 8.x for Drupal 10 default branch on Gitlab

Problem/Motivation

The release for the latest Drupal version (10) should be the default branch on Gitlab, currently it's Drupal 7.

• Drupal 7: https://git.drupalcode.org/project/smtp
• Drupal 10: https://git.drupalcode.org/project/smtp/-/tree/8.x-1.x

Steps to reproduce

Clone the module with Git, assuming you'll get the 8.x branch. Grep for a string from the UI, don't find it, and realize you're on Drupal 7 branch:

$ grep -ir "Set SMTP as the default mailsystem" <<< No result
$ git branch -a
* 7.x-1.x
  remotes/origin/4.6.x-1.x
  remotes/origin/4.7.x-1.x
[...]

Proposed resolution

Make 8.x the default branch on Gitlab.

Remaining tasks

User interface changes

API changes

Data model changes