R1:7aebd2388f7c

Remove monospaced font preference global defaults

Summary: Fixes T7764. These settings have low utility, are no longer used by default, have become less useful on modern Windows which has a better selection of available fonts, and will eventually be subsumed (at least, for the most part) by T4103.

Test Plan:
- Grepped for strings.
- Viewed settings.
- Changed font to "24px impact".
- Viewed diffs with default and custom font.

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: chad…