[ci] fix(aws): remove unused pip installation statement (#172)

Author: mariot

aws/Dockerfile

@@ -38,7 +38,6 @@ ARG PYOAEV_GIT_BRANCH_OVERRIDE
 RUN if [[ ${PYOAEV_GIT_BRANCH_OVERRIDE} ]] ; then \
         echo "Forcing specific version of client-python" && \
         apk add --no-cache git && \
-        pip install --upgrade pip==${PIP_VERSION} && \
         pip install pip3-autoremove && \
         pip-autoremove pyoaev -y && \
         pip install git+https://github.com/OpenAEV-Platform/client-python@${PYOAEV_GIT_BRANCH_OVERRIDE} ; \