[fxbug.dev] Migrate bug numbers

This changes fxbug.dev/ URLs from Monorail bug numbers to the new
Fuchsia Issue Tracker numbers.

The migration to the new issue tracker was announced here:
https://groups.google.com/a/fuchsia.dev/g/announce/c/GOYfJozEqmk/m/qsGsaJ7UAAAJ

Bug: 298074672
Change-Id: Ib4ddfeb1546c775df9e8f30a08244cd914b3f165
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/freetype2/+/980263
Reviewed-by: Ian McKellar <ianloic@google.com>