chore(deps): update docker.elastic.co/elastic-agent/elastic-agent docker tag to v9.1.1 (elastic#1238)

Co-authored-by: elastic-renovate-prod[bot] <174716857+elastic-renovate-prod[bot]@users.noreply.github.com>

Author: elastic-renovate-prod[bot]

.github/workflows/copilot-setup-steps.yml

@@ -60,7 +60,7 @@ jobs:
           - 5601:5601
         options: --health-cmd="curl http://localhost:5601/api/status" --health-interval=10s --health-timeout=5s --health-retries=10
       fleet:
-        image: docker.elastic.co/elastic-agent/elastic-agent:9.1.0@sha256:add63bc9d450c29b9e8bb462e4295fa2ec725db394f372fa392213aad5603553
+        image: docker.elastic.co/elastic-agent/elastic-agent:9.1.1@sha256:0a1eeae3aa36d4195f307e98d5e4c16006653dc3e164a17649815e2a2fc4fb13
         env:
           SERVER_NAME: fleet
           FLEET_ENROLL: "1"