use beta agent for mise default test

Author: burmudar

.buildkite/pipeline.yaml

@@ -1,27 +1,23 @@
+agents:
+  queue: beta
 steps:
   - label: ":k8s:"
     command: .buildkite/verify-yaml.sh
-    agents: { queue: standard }
 
   - label: ":k8s:"
     command: .buildkite/verify-label.sh
-    agents: { queue: standard }
 
   - label: ":k8s:"
     command: .buildkite/verify-rbac-labels.sh
-    agents: { queue: standard }
 
   - label: ":git: :sleuth_or_spy:"
     command: .buildkite/verify-release/verify-release.sh
-    agents: { queue: standard }
 
   - label: ":k8s: :sleuth_or_spy:"
     command: .buildkite/check-image-names.sh
-    agents: { queue: standard }
 
   - label: ":k8s:"
     command: .buildkite/verify-overlays.sh
-    agents: { queue: standard }
 
   # Please keep in mind that the release manifest uses specific branch names when creating releases.
   # Therefore, if you update them, or if you decide to change how we detect what kind of build we're dealing