Update the gating control files

Use a newer syntax found in another example package.  I am still sort
of figuring out how the script: syntax works.

Signed-off-by: David Cantrell <dcantrell@redhat.com>

gating.yaml

@@ -3,4 +3,4 @@ product_versions:
   - rhel-10
 decision_context: osci_compose_gate
 rules:
-  - !PassingTestCaseRule {test_case_name: osci.brew-build.tier0.functional}
+  - !PassingTestCaseRule {test_case_name: osci.brew-build./plans/forge-srpm-macros.functional}