Merge pull request #160 from lablup/dependabot/pip/python-ff/tensorflow-gpu-2.4.0

Bump tensorflow-gpu from 1.13.1+nv to 2.4.0 in /python-ff

Author: hephaex

python-ff/requirements.txt

@@ -80,7 +80,7 @@ six==1.12.0
 syntax
 tensorboard==1.13.1
 tensorflow-estimator==1.13.0
-tensorflow-gpu==1.13.1+nv
+tensorflow-gpu==2.4.0
 termcolor==1.1.0
 terminado==0.8.2
 testpath==0.4.2