chore: rename reference-architecture to reference-architectures and update links (#114)

Author: piyush117

ibm_catalog.json

@@ -16,10 +16,10 @@
             "diagrams": [
               {
                 "diagram": {
-                  "url": "https://raw.githubusercontent.com/terraform-ibm-modules/stack-retrieval-augmented-generation/main/reference-architecture/RAG%20Pattern%20v2-part-2.svg",
+                  "url": "https://raw.githubusercontent.com/terraform-ibm-modules/stack-retrieval-augmented-generation/main/reference-architectures/RAG%20Pattern%20v2-part-2.svg",
                   "caption": "sd",
                   "type": "image/svg+xml",
-                  "thumbnail_url": "https://raw.githubusercontent.com/terraform-ibm-modules/stack-retrieval-augmented-generation/main/reference-architecture/RAG%20Pattern%20v2-part-2.svg"
+                  "thumbnail_url": "https://raw.githubusercontent.com/terraform-ibm-modules/stack-retrieval-augmented-generation/main/reference-architectures/RAG%20Pattern%20v2-part-2.svg"
                 },
                 "description": "ds"
               }