welcome page: remove background in active window when plugin is disabled

Before the change in the plugin enabling would only be effective on
next program start.
1 job for !99 with removewelcomepageondisabling in 60 minutes (queued for 15 minutes and 23 seconds)
detached
Status Job ID Name Coverage
  Build
failed #30687
linux kf5-qt5 qt5.12

01:00:00

 
Name Stage Failure
failed
linux kf5-qt5 qt5.12 Build The script exceeded the maximum execution time set for the job
Unregistering type class 4
Unregistering type class 3
Unregistering type class 6
Unregistering type class 5
Unregistering type class 2

Start 79: test_gdbprinters
Pulling docker image gitlab/gitlab-runner-helper:x86_64-ac8e767a ...
ERROR: Job failed: execution took longer than 1h0m0s seconds