MNT Fix unit test

[emteknetnz]

Issue silverstripe/.github#320

Note that while this doesn't show up in CI until CMS 6, it can be replicated on a CMS 5.3 sink install with --testsuite framework-core --filter="SecurityDefaultAdminTest|VersionedMemberAuthenticatorTest"

Fixes https://github.com/silverstripe/recipe-kitchen-sink/actions/runs/11393429390/job/31701681778

1) SilverStripe\Security\Tests\VersionedMemberAuthenticatorTest::testAuthenticateAgainstLiveStage BadMethodCallException: Object->__call(): the method 'publishSingle' does not exist on 'SilverStripe\Security\Member'

This is a hard to reproduce issue where if you run VersionedMemberAuthenticatorTest AND another test that includes $usesDatabase = true or a fixture file, and you're using kitchen-sink, you'll get the above error. However if you only run VersionedMemberAuthenticatorTest it'll be fine.

CI failure is unrelated and will be fixed in silverstripe/gha-ci#158

[GuySartorelli]

For the sake of tracing this back:
This replaces #11437 which was originally part of #11432 (there's some comments there related to this broken build)

[GuySartorelli]

This still feels like we're just masking a regression, so I'm going to spend 30mins or so seeing if I can find the root cause of this.

[GuySartorelli]

Turns out this failure isn't new - it happens locally on 5.2 as well! Though I can't explain why it hasn't been showing in CI runs for CMS 5. I tried PHP 8.1 and 8.2 and it failed on both of those locally.

This does seem unique to some combination of unit testing and modifying the extension set at runtime - the former of which we'd just resolve somewhere in SapphireTest or one of the TestState classes and wouldn't affect production code, and the latter of which is heavily discouraged.
Because of that, I'm not spending more time on this. It still doesn't feel great, but until/unless it crops up again somewhere else I think this workaround is okay for now.

[GuySartorelli]

One small change