Update pull-requests.json from main (elastic#39548)

This commit updates the pull-requests.json file for the BK PR Bot from
main. It's not consulted in any way, but it reduces conflicts with
backports that include it.

.buildkite/pull-requests.json

@@ -5,23 +5,23 @@
             "pipelineSlug": "beats",
             "allow_org_users": true,
             "allowed_repo_permissions": ["admin", "write"],
-            "allowed_list": [ ],
+            "allowed_list": ["dependabot[bot]", "mergify[bot]"],
             "set_commit_status": true,
             "build_on_commit": true,
             "build_on_comment": true,
-            "trigger_comment_regex": "^(?:(?:buildkite\\W+)?(?:build|test)\\W+(?:this|it))|^/test$",
-            "always_trigger_comment_regex": "^(?:(?:buildkite\\W+)?(?:build|test)\\W+(?:this|it))|^/test$",
-            "skip_ci_labels": [ ],
+            "trigger_comment_regex": "^/(?:test)",
+            "always_trigger_comment_regex": "^/(?:test)",
+            "skip_ci_labels": ["skip-ci"],
             "skip_target_branches": [ ],
             "skip_ci_on_only_changed": [ ],
             "always_require_ci_on_changed": [ ]
         },
         {
             "enabled": true,
-            "pipeline_slug": "beats-xpack-elastic-agent",
+            "pipelineSlug": "beats-xpack-elastic-agent",
             "allow_org_users": true,
             "allowed_repo_permissions": ["admin", "write"],
-            "allowed_list": [ ],
+            "allowed_list": ["dependabot[bot]", "mergify[bot]"],
             "set_commit_status": true,
             "build_on_commit": true,
             "build_on_comment": true,