Mac: Remove use of deprecated font APIs
Mac: Remove use of deprecated font APIs

Remove use of CGContextSelectFont CGContextShowTextAtPoint APIs.
Verified that the new calls create the same pixel value for the
smoothing test as before.

Also remove workarounds for 10.6, because it is not supported anymore.

BUG=skia:5803
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2395613002

Review-Url: https://codereview.chromium.org/2395613002

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