add help

Author: jiasli

src/azure-cli/azure/cli/command_modules/role/_help.py

@@ -854,9 +854,10 @@
 type: command
 short-summary: Delete a role definition.
 examples:
-  - name: Delete a role definition. (autogenerated)
-    text: az role definition delete --name MyRole
-    crafted: true
+  - name: Delete a role definition by roleName.
+    text: az role definition delete --scope /subscriptions/00000000-0000-0000-0000-000000000000 --name MyRole
+  - name: Delete a role definition by name (GUID).
+    text: az role definition delete --scope /subscriptions/00000000-0000-0000-0000-000000000000 --name 00000000-0000-0000-0000-000000000000
 """
 
 helps['role definition list'] = """