mergify: support auto-merge for bk.integration-fips.pipeline.yml (#8468)

Support for other type of bk pipelines, see https://github.com/elastic/elastic-agent/pull/8465/checks?check_run_id=43966486237

Author: v1v

.mergify.yml

@@ -33,7 +33,7 @@ pull_request_rules:
     conditions:
       - author=github-actions[bot]
       - check-success=buildkite/elastic-agent
-      - files~=^.buildkite/(pipeline.yml|bk.integration.pipeline.yml)$
+      - files~=^.buildkite/(pipeline.yml|bk.integration.pipeline.yml|.buildkite/bk.integration-fips.pipeline.yml)$
       - head~=^updatecli_.*
       - "#approved-reviews-by>=1"
     actions: