ref(github-enterprise): Remove fully-GA github.com source flag registration

[tnt-sentry]

Final step of the three-PR flagpole removal for organizations:github-enterprise-github-com-source. Drop the manager.add(...) registration (and its comment) from src/sentry/features/temporary.py.

Sequence:

1. chore(github-enterprise): Remove fully-GA github.com source flag checks #116385 — remove the features.has(...) call sites + tests (backend)
2. getsentry/sentry-options-automatorfix(owners): allow out of app frames #7964 — remove the flagpole config block
3. This PR — remove the registration

⚠️ Do not merge until #7964 has merged AND deployed. Landing this earlier would log warnings about an unknown feature key from the still-live options config.

[github-actions]

Backend Test Failures

Failures on e368ab2 in this run:

tests/sentry/api/endpoints/test_project_trace_item_details.py::test_convert_rpc_attribute_to_json_serializes_known_string_array_without_array_flag — log

[gw0] linux -- Python 3.13.1 /home/runner/work/sentry/sentry/.venv/bin/python3
tests/sentry/api/endpoints/test_project_trace_item_details.py:18: in test_convert_rpc_attribute_to_json_serializes_known_string_array_without_array_flag
    assert result == [
E   assert [] == [{'name': 'ge...nt output"]'}]
E     
E     Right contains one more item: �[0m{�[33m'�[39;49;00m�[33mname�[39;49;00m�[33m'�[39;49;00m: �[33m'�[39;49;00m�[33mgen_ai.output.messages�[39;49;00m�[33m'�[39;49;00m, �[33m'�[39;49;00m�[33mtype�[39;49;00m�[33m'�[39;49;00m: �[33m'�[39;49;00m�[33mstr�[39;49;00m�[33m'�[39;49;00m, �[33m'�[39;49;00m�[33mvalue�[39;49;00m�[33m'�[39;49;00m: �[33m'�[39;49;00m�[33m[�[39;49;00m�[33m"�[39;49;00m�[33massistant output�[39;49;00m�[33m"�[39;49;00m�[33m]�[39;49;00m�[33m'�[39;49;00m}�[90m�[39;49;00m
E     
E     Full diff:
E     �[0m�[92m+ []�[39;49;00m�[90m�[39;49;00m
E     �[91m- [�[39;49;00m�[90m�[39;49;00m
E     �[91m-     {�[39;49;00m�[90m�[39;49;00m
E     �[91m-         'name': 'gen_ai.output.messages',�[39;49;00m�[90m�[39;49;00m
E     �[91m-         'type': 'str',�[39;49;00m�[90m�[39;49;00m
E     �[91m-         'value': '["assistant output"]',�[39;49;00m�[90m�[39;49;00m
E     �[91m-     },�[39;49;00m�[90m�[39;49;00m
E     �[91m- ]�[39;49;00m�[90m�[39;49;00m

tests/sentry/api/endpoints/test_project_trace_item_details.py::TestReplacementAttributeFiltering::test_replacement_array_shown_when_no_deprecated_source — log

[gw1] linux -- Python 3.13.1 /home/runner/work/sentry/sentry/.venv/bin/python3
tests/sentry/api/endpoints/test_project_trace_item_details.py:123: in test_replacement_array_shown_when_no_deprecated_source
    assert len(result) == 1
E   assert 0 == 1
E    +  where 0 = len([])

tests/sentry/api/endpoints/test_project_trace_item_details.py::test_convert_rpc_attribute_to_json_exposes_array_with_array_flag — log

[gw1] linux -- Python 3.13.1 /home/runner/work/sentry/sentry/.venv/bin/python3
tests/sentry/api/endpoints/test_project_trace_item_details.py:67: in test_convert_rpc_attribute_to_json_exposes_array_with_array_flag
    assert result == [
E   AssertionError: assert [{'name': 'ta...ant output']}] == [{'name': 'ge...ant output']}]
E     
E     At index 0 diff: �[0m{�[33m'�[39;49;00m�[33mname�[39;49;00m�[33m'�[39;49;00m: �[33m'�[39;49;00m�[33mtags[gen_ai.output.messages,array]�[39;49;00m�[33m'�[39;49;00m, �[33m'�[39;49;00m�[33mtype�[39;49;00m�[33m'�[39;49;00m: �[33m'�[39;49;00m�[33marray�[39;49;00m�[33m'�[39;49;00m, �[33m'�[39;49;00m�[33mvalue�[39;49;00m�[33m'�[39;49;00m: [�[33m'�[39;49;00m�[33massistant output�[39;49;00m�[33m'�[39;49;00m]}�[90m�[39;49;00m != �[0m{�[33m'�[39;49;00m�[33mname�[39;49;00m�[33m'�[39;49;00m: �[33m'�[39;49;00m�[33mgen_ai.output.messages�[39;49;00m�[33m'�[39;49;00m, �[33m'�[39;49;00m�[33mtype�[39;49;00m�[33m'�[39;49;00m: �[33m'�[39;49;00m�[33marray�[39;49;00m�[33m'�[39;49;00m, �[33m'�[39;49;00m�[33mvalue�[39;49;00m�[33m'�[39;49;00m: [�[33m'�[39;49;00m�[33massistant output�[39;49;00m�[33m'�[39;49;00m]}�[90m�[39;49;00m
E     
E     Full diff:
E     �[0m�[90m �[39;49;00m [�[90m�[39;49;00m
E     �[90m �[39;49;00m     {�[90m�[39;49;00m
E     �[91m-         'name': 'gen_ai.output.messages',�[39;49;00m�[90m�[39;49;00m
E     �[92m+         'name': 'tags[gen_ai.output.messages,array]',�[39;49;00m�[90m�[39;49;00m
E     ?                  +++++                      +++++++�[90m�[39;49;00m
E     �[90m �[39;49;00m         'type': 'array',�[90m�[39;49;00m
E     �[90m �[39;49;00m         'value': [�[90m�[39;49;00m
E     �[90m �[39;49;00m             'assistant output',�[90m�[39;49;00m
E     �[90m �[39;49;00m         ],�[90m�[39;49;00m
E     �[90m �[39;49;00m     },�[90m�[39;49;00m
E     �[90m �[39;49;00m ]�[90m�[39;49;00m