www/firefox: update to 65.0

Backport a fix for WebRender on Wayland e.g.,

$ GDK_BACKEND=wayland MOZ_WEBRENDER=1 MOZ_ACCELERATED=1 firefox https://example.com/

Changes: https://www.mozilla.org/firefox/65.0/releasenotes/
PR: 233791
Security: b1f7d52f-fc42-48e8-8403-87d4c9d26229
MFH: 2019Q1
Differential Revision: https://reviews.freebsd.org/D18432