chore(deps): update docker.elastic.co/elasticsearch/elasticsearch docker tag to v7.17.21 (#4305)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/ci.yml

@@ -28,7 +28,7 @@ jobs:
           - 6379:6379
 
       elastic:
-        image: docker.elastic.co/elasticsearch/elasticsearch:7.17.20
+        image: docker.elastic.co/elasticsearch/elasticsearch:7.17.21
         env:
           network.host: "0.0.0.0"
           http.cors.enabled: "true"