Import the gating plan from test git

As it currently requires CRB, so I don't have to duplicate the
configuration in multiple places.

gating.yaml

@@ -3,4 +3,4 @@ product_versions:
   - rhel-10
 decision_context: osci_compose_gate
 rules:
-  - !PassingTestCaseRule {test_case_name: osci.brew-build./plans/tier1-internal.functional}
+  - !PassingTestCaseRule {test_case_name: osci.brew-build./plans/all-internal.functional}

plans.fmf

@@ -0,0 +1,5 @@
+/all-internal:
+  plan:
+    import:
+      url: https://pkgs.devel.redhat.com/git/tests/libpsl
+      name: /plans/all

plans/tier1-internal.fmf

@@ -1,10 +0,0 @@
-summary: Internal gating tests plan
-discover:
-  - name: Internal gating tests (libpsl)
-    how: fmf
-    url: https://pkgs.devel.redhat.com/git/tests/libpsl
-execute:
-    how: tmt
-adjust:
-    enabled: false
-    when: distro == centos-stream or distro == fedora