Remove unused KConfigXT usage

This was cautgh by my kconfig_compiler rework, it broke generating
the files for KDevelop, but the reason was that there was no
configurations at all in the kcfg file, and was also never used in
this specific class was never used in kdevelop.
1 job for !90 with remove_unused_code in 50 minutes and 6 seconds (queued for 1 second)
detached
Status Job ID Name Coverage
  Build
passed #28686
linux kf5-qt5 qt5.12

00:50:06

47.0%