Remove broken gating file

Currently the gating file prevents building:

    rharwood@eesha:~/krb5.fedora/rawhide$ fedpkg build
    Could not execute build: Found a gating.yaml file in your repo with additional Greenwave policies, but it is not valid.
    Please fix the file or skip this check using the option --skip-remote-rules-validation.
    Error response from Greenwave: YAML Parser Error: mapping values are not allowed here
      in "<unicode string>", line 2, column 18:
           product_versions:
                                ^
    rharwood@eesha:~/krb5.fedora/rawhide$

Patches to add it back will be considered if and only if they don't
break the build.

gating.yaml

@@ -1,6 +0,0 @@
- --- !Policy
- product_versions:
-   - rhel-9
- decision_context: osci_compose_gate
- rules:
-   - !PassingTestCaseRule {test_case_name: baseos-ci.brew-build.tier1.functional}