Fix CI

Problem/Motivation

Both the 2.x and the 8.x-1.x pipelines fail currently.

For example:

• 8.x-1.x: https://git.drupalcode.org/project/config_overlay/-/pipelines/339001
• 2.x: https://git.drupalcode.org/project/config_overlay/-/pipelines/334333

Concretely, see the failing jobs:

• 8.x-1.x: https://git.drupalcode.org/project/config_overlay/-/jobs/3358521
• 2.x: https://git.drupalcode.org/project/config_overlay/-/jobs/3307430

8.x-1.x fails because a Drupal 11 compatible version of Config Ignore (i.e. ^3) is currently not allowed.

2.x fails because the config_overlay_test_config_split test module is not compatible with Drupal 11.