remove poetry from dockerfile

packages/@aws-cdk/aws-lambda-python/test/lambda-handler-custom-build-docker-image/Dockerfile.build

@@ -9,9 +9,6 @@ RUN yum -q list installed rsync &>/dev/null || yum install -y rsync
 # Upgrade pip (required by cryptography v3.4 and above, which is a dependency of poetry)
 RUN pip install --upgrade pip
 
-# Install pipenv and poetry so we can create a requirements.txt if we detect pipfile or poetry.lock respectively
-RUN pip install pipenv poetry
-
 # Install the dependencies in a cacheable layer
 WORKDIR /var/dependencies
 COPY requirements.txt ./