MFH: r516091

print/harfbuzz: update to 2.6.4

Changes: https://github.com/harfbuzz/harfbuzz/releases/tag/2.6.4
ABI: https://abi-laboratory.pro/tracker/timeline/harfbuzz/
Reported by: GitHub (watch releases)
Approved by: ports-secteam blanket (required by Firefox 72)