fix(preprod): Expose PR comments feature flag to frontend API

[runningcode]

Set api_expose=True for the organizations:preprod-build-distribution-pr-comments
feature flag so the frontend <Feature> component can check it.

Without this, the flag is never included in the organization features response,
causing the PR comments toggle to never render on the settings page.

Related to this PR: #110051

And EME-796

[cameroncooke]

LGTM!

[github-actions]

Backend Test Failures

Failures on b7df5b3 in this run:

tests/sentry/relay/test_config.py::test_get_project_config[REGION] — log

tests/sentry/relay/test_config.py:133: in test_get_project_config
    insta_snapshot(cfg)
E   Failed: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
E   Snapshot /home/runner/work/sentry/sentry/tests/sentry/relay/snapshots/test_config/test_get_project_config/REGION.pysnap changed!
E   
E   
E   Re-run pytest with SENTRY_SNAPSHOTS_WRITEBACK=new and then use 'make review-python-snapshots' to review.
E   
E   Or: Use SENTRY_SNAPSHOTS_WRITEBACK=1 to update snapshots directly.
E   
E   
E   --- 
E   
E   +++ 
E   
E   @@ -156,6 +156,7 @@
E   
E          isEnabled: true
E          patterns:
E          - '*healthcheck*'
E   +      - '*health-check*'
E          - '*heartbeat*'
E          - '*/health{/,}'
E          - '*/healthy{/,}'
E   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[github-actions]

Backend Test Failures

Failures on 41b41d8 in this run:

tests/sentry/relay/test_config.py::test_get_project_config[REGION] — log

tests/sentry/relay/test_config.py:133: in test_get_project_config
    insta_snapshot(cfg)
E   Failed: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
E   Snapshot /home/runner/work/sentry/sentry/tests/sentry/relay/snapshots/test_config/test_get_project_config/REGION.pysnap changed!
E   
E   
E   Re-run pytest with SENTRY_SNAPSHOTS_WRITEBACK=new and then use 'make review-python-snapshots' to review.
E   
E   Or: Use SENTRY_SNAPSHOTS_WRITEBACK=1 to update snapshots directly.
E   
E   
E   --- 
E   
E   +++ 
E   
E   @@ -156,6 +156,7 @@
E   
E          isEnabled: true
E          patterns:
E          - '*healthcheck*'
E   +      - '*health-check*'
E          - '*heartbeat*'
E          - '*/health{/,}'
E          - '*/healthy{/,}'
E   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~