Remove BK PR Bot trigger for x-pack/heartbeat (#39014)

In preparation for the migration to a static
pipeline (#38845), this commit removes the
Buildkite PR Bot trigger for the pipeline.

.buildkite/pull-requests.json

@@ -95,22 +95,6 @@
             "skip_target_branches": [ ],
             "skip_ci_on_only_changed": [ ],
             "always_require_ci_on_changed": ["^x-pack/libbeat/.*", "^.buildkite/.*", "^go.mod", "^pytest.ini", "^dev-tools/.*", "^libbeat/.*", "^testing/.*", "^x-pack/libbeat/.*"]
-        },
-        {
-            "enabled": true,
-            "pipelineSlug": "beats-xpack-heartbeat",
-            "allow_org_users": true,
-            "allowed_repo_permissions": ["admin", "write"],
-            "allowed_list": [ ],
-            "set_commit_status": true,
-            "build_on_commit": true,
-            "build_on_comment": true,
-            "trigger_comment_regex": "^/test x-pack/heartbeat$",
-            "always_trigger_comment_regex": "^/test x-pack/heartbeat$",
-            "skip_ci_labels": [  ],
-            "skip_target_branches": [ ],
-            "skip_ci_on_only_changed": [ ],
-            "always_require_ci_on_changed": ["^x-pack/heartbeat/.*", "^.buildkite/.*", "^go.mod", "^pytest.ini", "^dev-tools/.*", "^libbeat/.*", "^testing/.*", "^x-pack/libbeat/.*"]
         }
     ]
 }