Drop prop-flags patch for root-9999

Patch fails starting from 5.34.23 and ROOT 6 master. Upstream offers configure-flags to set proper flags starting now => use these. See e.g. upstream's commit http://root.cern.ch/gitweb?p=root.git;a=commit;h=9963acbe3e425f23fb98447aa6db87e41a881751 and release-announcement for 5.34.23.