enchant2: update to 2.8.12

[reneeotten]

Description

• update to latest upstream version

Tested on

macOS 15.5 24F74 x86_64
Xcode 16.4 16F6

Verification

Have you

• followed our Commit Message Guidelines?
• squashed and minimized your commits?
• checked that there aren't other open pull requests for the same change?
• referenced existing tickets on Trac with full URL in commit message?
• checked your Portfile with port lint?
• tried existing tests with sudo port test?
• tried a full install with sudo port -vst install?
• tested basic functionality of all binary files?
• checked that the Portfile's most important variants haven't been broken?

[macportsbot]

Notifying maintainers:
@ryandesign for port enchant2.