remove unused header
remove unused header


Former-commit-id: 1a50fa9c3ced855eb790fd3856ea666d7fe9169e
clab/dynet,chunyang-wen/dynet,danielhers/dynet,chunyang-wen/dynet,xunzhang/dynet,danielhers/dynet,clab/dynet,xunzhang/dynet,shuheik/dynet,danielhers/dynet,xunzhang/dynet,clab/cnn,shuheik/dynet,danielhers/dynet,danielhers/dynet,shuheik/dynet,clab/dynet,clab/dynet,shuheik/dynet,clab/cnn,shuheik/dynet,clab/cnn,clab/dynet,clab/dynet,chunyang-wen/dynet,shuheik/dynet,xunzhang/dynet,danielhers/dynet,shuheik/dynet,chunyang-wen/dynet,danielhers/dynet,clab/dynet