[v5.1] Drop minikube CI test

At the time of this commit, on main this task includes:

```yaml
    # 2024-05-21: flaking almost constantly since March.
    skip: $CI == $CI
```

Disable the test entirely on this branch due to multiple failures,
difficulty debugging, lack of team expertise, and willpower to care.

Ref: https://cirrus-ci.com/task/4712403315720192

Signed-off-by: Chris Evich <[email protected]>

.cirrus.yml

@@ -930,23 +930,6 @@ rootless_system_test_task:
     main_script: *main
     always: *logs_artifacts
 
-
-minikube_test_task:
-    name: *std_name_fmt
-    alias: minikube_test
-    # Docs: ./contrib/cirrus/CIModes.md
-    only_if: *not_tag_magic
-    depends_on: *build
-    gce_instance: *standardvm
-    env:
-        <<: *stdenvars
-        TEST_FLAVOR: minikube
-        PRIV_NAME: rootless
-    clone_script: *get_gosrc
-    setup_script: *setup
-    main_script: *main
-    always: *logs_artifacts
-
 farm_test_task:
     name: *std_name_fmt
     alias: farm_test
@@ -1079,7 +1062,6 @@ success_task:
         - remote_system_test
         - rootless_remote_system_test
         - rootless_system_test
-        - minikube_test
         - farm_test
         - buildah_bud_test
         - upgrade_test