Explicitly use an Ubuntu agent on the JUnit step

Author: JoshMock

.buildkite/pipeline.yml

@@ -2,7 +2,6 @@ steps:
   - label: ":elasticsearch: :javascript: ES JavaScript ({{ matrix.nodejs }}) Test Suite: {{ matrix.suite }}"
     agents:
       provider: "gcp"
-      image: family/core-ubuntu-2204
     env:
       NODE_VERSION: "{{ matrix.nodejs }}"
       TEST_SUITE: "{{ matrix.suite }}"
@@ -22,8 +21,11 @@ steps:
   - wait: ~
     continue_on_failure: true
   - label: ":junit: Test results"
+    agents:
+      provider: "gcp"
+      image: family/core-ubuntu-2204
     plugins:
-      - junit-annotate#v1.9.0:
+      - junit-annotate#v2.4.1:
           artifacts: "junit-output/junit-*.xml"
           job-uuid-file-pattern: 'junit-(.*).xml'
           fail-build-on-error: true