MFH: r525108 r525155 r525478 r525512

www/firefox: update to 73.0

Changes: https://www.mozilla.org/firefox/73.0/releasenotes/
PR: 243295
Security: 802e3138-b8af-4a89-a908-f103107e64b4
Approved by: ports-secteam blanket
Differential Revision: https://reviews.freebsd.org/D23146