Update branch for Spring Apps repository

As the Azure Spring Apps Reference Architecture team transitions the contents of the repository to support a Landing Zone Accelerator centric design, this commit changes the source branch for the repository reference to a protected branch in the repository. This change will enable continued development in the main branch without disrupting the referenced artifacts in the Azure documentation.

Author: kriation

.openpublishing.publish.config.json

@@ -755,7 +755,7 @@
     {
       "path_to_root": "azure-spring-apps-reference-architecture",
       "url": "https://github.com/Azure/azure-spring-apps-reference-architecture",
-      "branch": "main",
+      "branch": "reference-architecture",
       "branch_mapping": {}
     },
     {