[jupyterhub] use gpu enabled tensorflow 2

jupyterhub/base/Dockerfile

@@ -93,7 +93,7 @@ RUN mkdir -p /usr/local/venv && \
     python${PYTHON_VERSION} -m pip install --upgrade \
         pip==${PYTHON_PIP_VERSION} \
         setuptools==${PYTHON_SETUPTOOLS_VERSION} && \
-    pip install tensorflow==2.3.1 && \
+    pip install tensorflow-gpu==2.3.1 && \
     pip install \
         wheel \
         black \