Remove version numbers from requirements.

requirements.txt

-absl-py==0.12.0
-astunparse==1.6.3
-cachetools==4.2.1
-certifi==2020.12.5
-cffi==1.14.5
-chardet==4.0.0
-cloudpickle==1.6.0
-gast==0.3.3
-google-auth==1.29.0
-google-auth-oauthlib==0.4.4
-google-pasta==0.2.0
-grpcio==1.37.0
-h5py==2.10.0
-horovod==0.20.3
-hpc4neuro @ git+https://gitlab.version.fz-juelich.de/hpc4ns/hpc4neuro.git@57a560b4085dba2ba3262d4d3238ef70991be877
-idna==2.10
-Keras-Preprocessing==1.1.2
-Markdown==3.3.4
-mpi4py==3.0.3
-numpy==1.18.5
-oauthlib==3.1.0
-opt-einsum==3.3.0
-protobuf==3.15.8
-psutil==5.8.0
-pyasn1==0.4.8
-pyasn1-modules==0.2.8
-pycparser==2.20
-PyYAML==5.4.1
-requests==2.25.1
-requests-oauthlib==1.3.0
-rsa==4.7.2
-six==1.15.0
-tensorboard==2.5.0
-tensorboard-data-server==0.6.0
-tensorboard-plugin-wit==1.8.0
-tensorflow==2.3.1
-tensorflow-estimator==2.3.0
-termcolor==1.1.0
-urllib3==1.26.4
-Werkzeug==1.0.1
-wrapt==1.12.1
+absl-py
+astunparse
+cachetools
+certifi
+cffi
+chardet
+cloudpickle
+gast
+google-auth
+google-auth-oauthlib
+google-pasta
+grpcio
+h5py
+horovod
+idna
+Keras-Preprocessing
+Markdown
+mpi4py
+numpy
+oauthlib
+opt-einsum
+protobuf
+psutil
+pyasn1
+pyasn1-modules
+pycparser
+PyYAML
+requests
+requests-oauthlib
+rsa
+six
+tensorboard
+tensorboard-data-server
+tensorboard-plugin-wit
+tensorflow
+tensorflow-estimator
+termcolor
+urllib3
+Werkzeug
+wrapt