Fix OpenAPI Generator not being version 7.21.0 in ci

Author: C0D3-M4513R

.github/workflows/ci.yaml

@@ -40,7 +40,7 @@ jobs:
       - name: Install OpenAPI Generator CLI
         run: npm install @openapitools/openapi-generator-cli
       - name: Set OpenAPI Generator version
-        run: ./node_modules/\@openapitools/openapi-generator-cli/main.js version-manager set 7.20.0
+        run: ./node_modules/\@openapitools/openapi-generator-cli/main.js version-manager set 7.21.0
       - name: Set up JDK 20
         uses: actions/setup-java@v4
         with: