Fix python doc build issue (#16630)
Fix python doc build issue (#16630)

* pin the pip versions

* remove nbconvert comment

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