.buildkite/auditbeat - Run integ tests on non-PR builds (#41919)

We want to run Auditbeat integration tests regularly on non-PR (main
branch builds).

This will help ensure problems are not missed in the various integration
test systems, and help prepare for adding Ubuntu 24.04 to the list of
officially supported systems.

.buildkite/auditbeat/auditbeat-pipeline.yml

@@ -203,7 +203,7 @@ steps:
     steps:
       - label: ":ubuntu: Auditbeat: Ubuntu x86_64 Integration Tests -- {{matrix.image}}"
         key: "auditbeat-extended-integ-tests"
-        if: build.env("GITHUB_PR_LABELS") =~ /.*integrations.*/
+        if: build.env("BUILDKITE_PULL_REQUEST") == "false" || build.env("GITHUB_PR_LABELS") =~ /.*integrations.*/
         command: |
           set -euo pipefail
           cd auditbeat
@@ -236,7 +236,7 @@ steps:
 
       - label: ":ubuntu: Auditbeat: Ubuntu arm64 Integration Tests -- {{matrix.image}}"
         key: "auditbeat-extended-arm64-integ-tests"
-        if: build.env("GITHUB_PR_LABELS") =~ /.*integrations.*/
+        if: build.env("BUILDKITE_PULL_REQUEST") == "false" || build.env("GITHUB_PR_LABELS") =~ /.*integrations.*/
         command: |
           set -euo pipefail
           cd auditbeat