build(deps): bump openapitools/openapi-generator-cli

Bumps openapitools/openapi-generator-cli from v7.20.0 to v7.21.0.

---
updated-dependencies:
- dependency-name: openapitools/openapi-generator-cli
  dependency-version: v7.21.0
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

compose.yml

@@ -1,7 +1,7 @@
 ---
 services:
   gen:
-    image: docker.io/openapitools/openapi-generator-cli:v7.20.0
+    image: docker.io/openapitools/openapi-generator-cli:v7.21.0
     restart: never
     network_mode: none
     volumes: