Fixing dockerfile bug, && on both end and beginning of the line (#254)

Author: sboshin

docker/2.0.0/py3/Dockerfile.cpu

@@ -106,7 +106,7 @@ RUN ${PIP} install --no-cache-dir -U \
     requests==2.22.0 \
     awscli==1.16.196 \
     mpi4py==3.0.2 \
-    "sagemaker-tensorflow>=2.0,<2.1" && \
+    "sagemaker-tensorflow>=2.0,<2.1" \
     # Let's install TensorFlow separately in the end to avoid
     # the library version to be overwritten
  && ${PIP} install --force-reinstall --no-cache-dir -U ${TF_URL} \