Drop dist.abicheck from gating tests.

Taskotron reached EOL so the test can't be run anymore:
https://fedoraproject.org/wiki/Taskotron/Tasks/dist.abicheck

gating.yaml

@@ -4,5 +4,4 @@ product_versions:
   - fedora-rawhide
 decision_context: bodhi_update_push_stable
 rules:
-  - !PassingTestCaseRule {test_case_name: dist.abicheck}
   - !PassingTestCaseRule {test_case_name: fedora-ci.koji-build.tier0.functional}