Fix schema_version mismatch in ai-plugin.json and clear tenant IDs

Align schema_version with $schema URL (v2.4 → v2.1) and restore empty
tenant-specific values in .env.dev.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: KatT-AI

samples/da-sharepoint-data-manager/appPackage/ai-plugin.json

@@ -1,6 +1,6 @@
 {
     "$schema": "https://aka.ms/json-schemas/copilot-extensions/v2.1/plugin.schema.json",
-    "schema_version": "v2.4",
+    "schema_version": "v2.1",
     "name_for_human": "Microsoft Learn Search",
     "description_for_human": "Search official Microsoft documentation for SharePoint and Microsoft 365 guidance",
     "contact_email": "publisher-email@example.com",

samples/da-sharepoint-data-manager/env/.env.dev

@@ -8,4 +8,4 @@ APP_NAME_SUFFIX=dev
 TEAMS_APP_ID=
 TEAMS_APP_TENANT_ID=
 M365_TITLE_ID=
-M365_APP_ID=
+M365_APP_ID=