We are soon going to remove the support for Python 3.5. So remove
the CI job now.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20200922070441.48844-1-thuth@redhat.com>
Message-Id: <20200925154027.12672-9-alex.bennee@linaro.org>