Update relast-preprocessor to newest version.

- remove mustache (reuse the submodule of the preprocessor)
- align attributes and build logic to changes in preprocessor
4 jobs for 27-parsing-fails-if-no-trailing-newline in 11 minutes and 18 seconds (queued for 1 second)
Status Name Job ID Coverage
  Build
passed build #22325

00:02:50

 
  Test
passed test #22326

00:08:28

 
  Ragdoc Build
passed ragdoc_build #22327

00:00:33

 
  Ragdoc View
passed ragdoc_view #22328

00:04:21