[ci] Remove 8.13 (#186377)

8.14 is released.  8.13 tests do not need to run now.

.buildkite/pipeline-resource-definitions/kibana-on-merge.yml

@@ -25,7 +25,7 @@ spec:
         REPORT_FAILED_TESTS_TO_GITHUB: 'true'
         ELASTIC_SLACK_NOTIFICATIONS_ENABLED: 'true'
       allow_rebuilds: true
-      branch_configuration: main 7.17 8.13 8.14
+      branch_configuration: main 7.17 8.14
       default_branch: main
       repository: elastic/kibana
       pipeline_file: .buildkite/pipelines/on_merge.yml

versions.json

@@ -13,12 +13,6 @@
       "currentMajor": true,
       "previousMinor": true
     },
-    {
-      "version": "8.13.5",
-      "branch": "8.13",
-      "currentMajor": true,
-      "previousMinor": true
-    },
     {
       "version": "7.17.23",
       "branch": "7.17",