CI doesn't catch changes in autogenerated documentation

[David Kastrup]

I just had the pipeline run

https://gitlab.com/lilypond/lilypond/-/pipelines/393509219

finish.  This change adds engravers/performers including engraver
information, stuff that is extracted into the IR.  It also adds a
regtest.

However, the CI decided to skip generation of the documentation which
presumably means that the documentation will not be updated until after
some other change adds documentation.

-- 
David Kastrup