update docs for container exec

https://github.com/docker/docker/pull/11665 This PR changed container
exec API response, we need docs updated.

Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>

docs/sources/reference/api/docker_remote_api.md

@@ -75,12 +75,16 @@ Builds can now set resource constraints for all containers created for the build
 **New!**
 (`CgroupParent`) can be passed in the host config to setup container cgroups under a specific cgroup.
 
-
 `POST /build`
 
 **New!**
 Closing the HTTP request will now cause the build to be canceled.
 
+`POST /containers/(id)/exec`
+
+**New!**
+Add `Warnings` field to response.
+
 ## v1.17
 
 ### Full Documentation

docs/sources/reference/api/docker_remote_api_v1.18.md

@@ -1832,6 +1832,7 @@ Sets up an exec instance in a running container `id`
 
         {
              "Id": "f90e34656806"
+             "Warnings":[]
         }
 
 Json Parameters: