Fix the D11 compatibility of 2.x-dev [#3570690]

Problem/Motivation

2.2.0 is marked compatible with Drupal 11, but the 2.x-dev branch doesn't have the changes to the .info.yml file that mark the module as compatible with Drupal 11. They were only merged into 2.2.x-dev (which isn't a version that shows in the Drupal.org version dropdown for issues.)

Steps to reproduce

This can be seen in the GitLab CI jobs for 2.2.x:

https://git.drupalcode.org/project/key_auth/-/jobs/4598854

A user also reported this issue (see below).

The dev release is currently not compatible with Drupal 11. Was getting a WSOD with a site updated to Drupal core 11.3 and PHP 8.4.

ddev composer require 'drupal/key_auth:2.x-dev@dev'
./composer.json has been updated
Running composer update drupal/key_auth
Gathering patches for root package.
Loading composer repositories with package information
Updating dependencies
Your requirements could not be resolved to an installable set of packages.

Problem 1
- Root composer.json requires drupal/key_auth 2.x-dev@dev -> satisfiable by drupal/key_auth[2.x-dev (alias of dev-2.x)].
- drupal/key_auth dev-2.x requires drupal/core ^9.5 || ^10 -> found drupal/core[9.5.0-beta1, ..., 9.5.x-dev, 10.0.0-alpha1, ..., 10.6.x-dev] but the package is fixed to 11.3.2 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command.
- drupal/key_auth 2.x-dev is an alias of drupal/key_auth dev-2.x and thus requires it to be installed too.

Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.

Installation failed, reverting ./composer.json and ./composer.lock to their original content.

Copied from https://www.drupal.org/project/key_auth/issues/3528017#comment-16448675

Proposed resolution

Merge 2.2.x-dev into 2.x-dev and use 2.x-dev as the dev branch, as that's what is marked as the dev branch for 2.2.0 and 2.1.0 on the module's front page, and it's the target branch for merge requests in issues.