kdevplatform: remove About data feature

With KDevPlatform no longer a stand-alone product, but effectively
only an internal architecture platform of KDevelop, the About data
and the About KDevPlatform dialog no longer make sense

Any author information is merged with the one of the KDevelop app,
which it already almost was a subset of.
1 job for !84 with removeplatformaboutdata in 60 minutes (queued for 26 minutes and 17 seconds)
Status Job ID Name Coverage
failed #27462
linux kf5-qt5 qt5.12


Name Stage Failure
linux kf5-qt5 qt5.12 Build The script exceeded the maximum execution time set for the job
kdeinit5: Fatal IO error: client killed
kdeinit5: sending SIGHUP to children.
after 18806 requests (18806 known processed) with 0 events remaining.
klauncher: Exiting on signal 1
kdeinit5: sending SIGTERM to children.
kdeinit5: Exit.
$ python3 -u $CI_TOOLING/helpers/print-lcov-results.py --product $PRODUCT --project $PROJECT --branchGroup $BRANCH_GROUP --platform $PLATFORM
Pulling docker image gitlab/gitlab-runner-helper:x86_64-ac8e767a ...
ERROR: Job failed: execution took longer than 1h0m0s seconds