Update the OBO README.md file and application.yml (Azure#18417)

Author: ZhuXiaoBing-cn

sdk/spring/azure-spring-boot-samples/azure-spring-boot-sample-active-directory-resource-server-obo/README.md

@@ -70,9 +70,6 @@ See [OAuth 2.0 On-Behalf-Of flow] for more information about OBO.
 ```yaml
 azure:
   activedirectory:
-    resource-server:
-      obo:
-        enabled: true
     client-id: <Web-API-A-client-id>
     client-secret: <Web-API-A-client-secret>
     tenant-id: <tenant-id-registered-by-application>

sdk/spring/azure-spring-boot-samples/azure-spring-boot-sample-active-directory-resource-server-obo/src/main/resources/application.yml

@@ -3,9 +3,6 @@ server:
 
 azure:
   activedirectory:
-    resource-server:
-      obo:
-        enabled: true
     client-id: <Web-API-A-client-id>
     client-secret: <Web-API-A-client-secret>
     tenant-id: <Tenant-id-registered-by-application>