YaST:Head - added Leap 15.5, removed Leap 15.3

Hello! I have added the openSUSE Leap 15.5 build target to YaST:Head OBS project. (https://build.opensuse.org/project/show/YaST:Head) And I removed the openSUSE Leap 15.3 build target because it is out of support (already for ~6 months) and to save some build resources. Enjoy :-) Ladislav -- Ladislav Slezák YaST Developer SUSE LINUX, s.r.o. Corso IIa Křižíkova 148/34 18600 Praha 8