update sa-token-doc/doc/oauth2/oauth2-server.md.

缺少 .setIsAutoMode(true) 会导致 {"code":500,"msg":"暂未开放的授权模式","data":null}

sa-token-doc/doc/oauth2/oauth2-server.md

@@ -47,7 +47,8 @@ public class SaOAuth2TemplateImpl extends SaOAuth2Template {
 					.setClientId("10001")
 					.setClientSecret("aaaa-bbbb-cccc-dddd-eeee")
 					.setAllowUrl("*")
-					.setContractScope("userinfo");
+					.setContractScope("userinfo")
+                                        .setIsAutoMode(true);
 		}
 		return null;
 	}