[packman] Dropping 11.4 and 12.2 repos on Packman

[Peter Linnell]

Hi all,

I am proposing to drop 11.4 and 12.2 from the Essentials and Multimedia
repos to save build power for PMBS.  Evergreen 11.4 is no longer going
to be maintained. 12.2 is end of life. 

I'm also proposing adding SLES 11 SP3 to replace the SLE 11 repo.

Any objections ?

Thanks,

Peter