chore: rename converged_infra tag to platform_engineering

Author: Harika-Ponna

ibm_catalog.json

@@ -5,7 +5,7 @@
       "name": "Mock-Stack",
       "product_kind": "solution",
       "tags": [
-        "converged_infra"
+        "platform_engineering"
       ],
       "offering_icon_url": "https://globalcatalog.cloud.ibm.com/api/v1/1082e7d2-5e2f-0a11-a3bc-f88a8e1931fc/artifacts/solution.svg",
       "flavors": [