Fix man file names for Flatpak builds
    
    ...to avoid failures like
    
    > error: File not found: /builddir/build/BUILDROOT/libvoikko-4.1.1-3.module_f31+8642+447c158d.x86_64/app/share/man/man1/voikkohyphenate.1.gz
    > error: File not found: /builddir/build/BUILDROOT/libvoikko-4.1.1-3.module_f31+8642+447c158d.x86_64/app/share/man/man1/voikkospell.1.gz
    > error: File not found: /builddir/build/BUILDROOT/libvoikko-4.1.1-3.module_f31+8642+447c158d.x86_64/app/share/man/man1/voikkogc.1.gz
    
    (<https://kojipkgs.fedoraproject.org//work/tasks/1577/43431577/build.log>) while
    building the LibreOffice flatpak.
    
    
    _uncompressed_manual_pages> states:  "The recommendation in the Fedora packaging
    guidelines is to have:
    
      %{_mandir}/man1/<command>.1*
    
    which is more robust against future changes to the RPM scripts to use different
    compression."