core: bump openapitools/openapi-diff from 2.1.5 to 2.1.6 in /scripts/api (#18400)

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

scripts/api/docker-compose.yml

@@ -1,7 +1,7 @@
 ---
 services:
   diff:
-    image: docker.io/openapitools/openapi-diff:2.1.5
+    image: docker.io/openapitools/openapi-diff:2.1.6
     restart: never
     network_mode: none
     volumes: