www/firefox: update to 71.0 Changes: https://www.mozilla.org/firefox/71.0/releasenotes/ PR: 241840 Security: 13b6433c-7aaf-477b-b96b-164924a005bb MFH: 2019Q4 Differential Revision: https://reviews.freebsd.org/D22296
head/Mk/bsd.gecko.mk