Remove gating.yaml to fix smoke test gating

The smoke test runs and passes under osci.brew-build.tier0.functional,
but gating.yaml expects results under a separate testcase (OSCI-8144).
Removing gating.yaml lets OSCI handle gating automatically via tier0.

Resolves: RHEL-177965 - https://redhat.atlassian.net/browse/RHEL-177965

gating.yaml

@@ -1,6 +0,0 @@
---- !Policy
-product_versions:
- - rhel-10
-decision_context: osci_compose_gate
-rules:
- - !PassingTestCaseRule {test_case_name: osci.brew-build./tests/tmt/plans/smoke}   # this is the testcase identifier, which OSCI pipeline uses