Fix warning in waitall doc (#13618)
Fix warning in waitall doc (#13618)


yajiedesign/mxnet,ptrendx/mxnet,sxjscience/mxnet,yajiedesign/mxnet,tlby/mxnet,ptrendx/mxnet,sxjscience/mxnet,apache/incubator-mxnet,szha/mxnet,sxjscience/mxnet,eric-haibin-lin/mxnet,reminisce/mxnet,zhreshold/mxnet,zhreshold/mxnet,ForkedReposBak/mxnet,szha/mxnet,leezu/mxnet,eric-haibin-lin/mxnet,yajiedesign/mxnet,tlby/mxnet,larroy/mxnet,leezu/mxnet,apache/incubator-mxnet,ForkedReposBak/mxnet,larroy/mxnet,tlby/mxnet,dmlc/mxnet,sxjscience/mxnet,yajiedesign/mxnet,ptrendx/mxnet,larroy/mxnet,leezu/mxnet,eric-haibin-lin/mxnet,eric-haibin-lin/mxnet,szha/mxnet,szha/mxnet,yajiedesign/mxnet,tlby/mxnet,ptrendx/mxnet,ForkedReposBak/mxnet,ptrendx/mxnet,reminisce/mxnet,sxjscience/mxnet,larroy/mxnet,leezu/mxnet,reminisce/mxnet,tlby/mxnet,szha/mxnet,leezu/mxnet,dmlc/mxnet,dmlc/mxnet,tlby/mxnet,eric-haibin-lin/mxnet,ptrendx/mxnet,leezu/mxnet,leezu/mxnet,szha/mxnet,sxjscience/mxnet,zhreshold/mxnet,eric-haibin-lin/mxnet,larroy/mxnet,apache/incubator-mxnet,apache/incubator-mxnet,larroy/mxnet,tlby/mxnet,szha/mxnet,yajiedesign/mxnet,tlby/mxnet,reminisce/mxnet,larroy/mxnet,DickJC123/mxnet,sxjscience/mxnet,yajiedesign/mxnet,szha/mxnet,sxjscience/mxnet,zhreshold/mxnet,ForkedReposBak/mxnet,larroy/mxnet,zhreshold/mxnet,eric-haibin-lin/mxnet,tlby/mxnet,ptrendx/mxnet,tlby/mxnet,dmlc/mxnet,larroy/mxnet,yajiedesign/mxnet,reminisce/mxnet,reminisce/mxnet,zhreshold/mxnet,yajiedesign/mxnet,leezu/mxnet,DickJC123/mxnet,zhreshold/mxnet,reminisce/mxnet,reminisce/mxnet,zhreshold/mxnet,reminisce/mxnet,dmlc/mxnet,ForkedReposBak/mxnet,dmlc/mxnet,reminisce/mxnet,ptrendx/mxnet,eric-haibin-lin/mxnet,DickJC123/mxnet,dmlc/mxnet,eric-haibin-lin/mxnet,sxjscience/mxnet,ForkedReposBak/mxnet,dmlc/mxnet,ForkedReposBak/mxnet,ForkedReposBak/mxnet,zhreshold/mxnet,dmlc/mxnet,szha/mxnet,ptrendx/mxnet,ForkedReposBak/mxnet,leezu/mxnet,ptrendx/mxnet,DickJC123/mxnet