Remove pointless background assignment

1 job for master in 13 minutes and 14 seconds
Status Job ID Name Coverage
  Build
failed #57129
flatpak
flatpak

00:13:14

 
Name Stage Failure
failed
flatpak Build
  run.
Call Stack (most recent call first):
CMakeLists.txt:10 (feature_summary)


-- Configuring incomplete, errors occurred!
See also "/run/build/kdelibs4support/_flatpak_build/CMakeFiles/CMakeOutput.log".
Error: module kdelibs4support: Child process exited with code 1
ERROR: Job failed: exit code 1