Log Message:
textproc/enchant2: Stop force-disabling apple spell

Before the freeze, I disabled all spellcheckers not covered by options
to avoid packaging failures and behavior changes from finding packages
that are installed and not declared dependencies.  It turns out one of
those not-declared dependencies was apple spell on mac, and the
package's PLIST.Darwin expects it always.

As a minimal fix in freeze, comment out the disabling of apple spell.
This will leave Darwin that is not macOS broken, but probably Darwin
without macOS is solidly at zero users.

As part of looking at the other supported spellcheckers for similar
issues, fold the comments in options about checkers supported in
enchant2 but not handled in options.mk to the main Makefile block that
disables them, removing comments about checkers no longer present in
the upstream sources.