support/testing/tests/package/sample_gst1_python.py: fix flake8 warnings

support/testing/tests/package/sample_gst1_python.py: fix flake8 warnings

Fixes the following flake8 warnings:

  support/testing/tests/package/sample_gst1_python.py:5:1: F401 'time' imported but unused
  support/testing/tests/package/sample_gst1_python.py:7:1: E402 module level import not at top of file
  support/testing/tests/package/sample_gst1_python.py:21:12: W292 no newline at end of file

For the E402 warning, we add a "noqa" marker, as we really want the
gi.require_version() to be before.

There is still one remaining warning to be fixed:

  support/testing/tests/package/sample_gst1_python.py:18:28: F821 undefined name 'on_message'

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>