Update qt6-macros to version 20210301 / rev 3 via SR 891892
    
    https://build.opensuse.org/request/show/891892
    by user cgiboudeaux + dimstar_suse
    - Remove the module name from the docs build targets.
      The modules now have 'docs' and 'install_docs' build targets. (forwarded request 891891 from cgiboudeaux)