Log Message:
cups{,-base}: Update print/cups{,-base} to 2.2.6

pkgsrc changes:
- s/ghostscript/cups-filters/ in MESSAGE (most missing parts needed to use
  non-PS printers are provided by print/cups-filters)
- Define GITHUB_PROJECT to just `cups' (not `cups-base', as PKGBASE).
  This fixes fetching of the distfile from the MASTER_SITES.

Changes:
CUPS v2.2.6
-----------
- DBUS notifications could crash the scheduler (Issue #5143)
- Added USB quirks rules for Canon MP540 and Samsung ML-2160 (Issue #5148)
- Fixed TLS cipher suite selection with GNU TLS (Issue #5145, Issue #5150)
- Localization updates (Issue #5152)