[rpm] Reinstate execute bits for setcaps helper script. Fixes JB#23021

While removing unused legacy files and scripts from timed rpm, the
chmod that makes setcaps-timed-qt5.sh executable was also removed
and timed lost the ability to change the system time.

Restore the lines that should not have been removed.
Merge pull request #54 from spiiroin/jb23021

[rpm] Reinstate execute bits for setcaps helper script. Fixes JB#23021