tests/docker: remove python2.7 from debian9-mxe

When it was based on debian8 which uses python-minimal, it needed this.
It no longer does.

Goodbye, python2.7.
Signed-off-by: NJohn Snow <jsnow@redhat.com>
Message-Id: <20190918222546.11696-1-jsnow@redhat.com>
[AJB: fixed up commit message]
Signed-off-by: NAlex Bennée <alex.bennee@linaro.org>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>

tests/docker/dockerfiles/debian9-mxe.docker

@@ -16,7 +16,6 @@ RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys C6BF758A33A3A276 &&
 RUN apt-get update && \
     DEBIAN_FRONTEND=noninteractive eatmydata \
     apt-get install -y --no-install-recommends \
-        libpython2.7-stdlib \
         $(apt-get -s install -y --no-install-recommends gw32.shared-mingw-w64 | egrep "^Inst mxe-x86-64-unknown-" | cut -d\  -f2)
 
-ENV PATH $PATH:/usr/lib/mxe/usr/bin/ 
+ENV PATH $PATH:/usr/lib/mxe/usr/bin/