Update python-seqdiag to version 3.0.0 / rev 6 via SR 980777
    
    https://build.opensuse.org/request/show/980777
    by user dirkmueller + dimstar_suse
    - update to 3.0.0:
      * Drop python3.6 support
      * Use funcparserlib-1.0.0a0 or newer to support new python versions
      * Allow to write multiline string via triple quotes (""" ... """)
      * Add "edge_label_margin" attribute to edges
      * Fix bugs
        - Fix #147: file existence disclosure using svg renderer
        - Separator does not support both default_fontsize and default_textcolor