py-gmpy2: drop py39 subport

[mndavidoff]

Description

py-gmpy2: drop py39 subport

Type(s)

• bugfix
• enhancement
• security fix

Tested on

macOS 15.7.1 24G231 arm64
Command Line Tools 26.0.0.0.1.1757719676

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?

[reneeotten]

it's a test dependency for "py39-scipy" so until that subport is removed you cannot get rid of the py39 subport here.

[reneeotten]

Closing this PR for now as it cannot be merged at this time.