www/chromium: Update to 87.0.4280.88

https://chromereleases.googleblog.com/2020/12/stable-channel-update-for-desktop.html

Changes: https://chromium.googlesource.com/chromium/src/+log/87.0.4280.67..87.0.4280.88?pretty=fuller&n=10000

Approved by: jrm
Differential Revision: https://reviews.freebsd.org/D27452