Docker: Python requirements are now managed in-tree

Neither mbed-host-tests nor mock are currently used.

Signed-off-by: Gilles Peskine <[email protected]>

tests/docker/bionic/Dockerfile

@@ -161,6 +161,4 @@ RUN cd /tmp \
 ENV GNUTLS_NEXT_CLI=/usr/local/gnutls-3.7.2/bin/gnutls-cli
 ENV GNUTLS_NEXT_SERV=/usr/local/gnutls-3.7.2/bin/gnutls-serv
 
-RUN pip3 install --no-cache-dir \
-    mbed-host-tests \
-    mock
+RUN scripts/min_requirements.py