Log Message:
Update cups-filters to 1.28.8

NEWS - OpenPrinting CUPS Filters v1.28.8 - 2021-03-25
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CHANGES IN V1.28.8

- libcupsfilters: Made check whether the driverless PPD to
  generate should be a fax out PPD more reliable (Issue #343).
- foomatic-rip: Options in the 5th command line argument of
  the CUPS filter command line are separated only by white
  space and not by comma, also make sure that an option "none"
  is not considered a custom page size (Issue #348).
- implicitclass: Raise timeout for cups-browsed's answer from
  20s to 60s (Pull request #346).
- libcupsfilters: In the PPD generator really give priority to
  Apple Raster against PDF (Issue #331).