revert pandas fix version for cnn_tools hash match

Author: vera121

python/requirements.txt

@@ -8,7 +8,7 @@ h5py>=2.2.0
 leveldb==0.20
 networkx==2.2
 nose>=1.3.0
-pandas
+pandas==0.24.0
 python-dateutil>=2.6.0
 protobuf>=2.5.0
 python-gflags>=2.0