bluez: Fix dictionnary key usage

This syntax is wrong, it generates the following error:
File "/usr/lib/python3/dist-packages/apertis_tests_lib/bluez.py", line
  557, in __show_menu
      name = str(i['org.bluez.Device1'].get(['Name'], address))
      TypeError: unhashable type: 'list'

Signed-off-by: Frédéric Dalleau <frederic.dalleau@collabora.co.uk>
Differential Revision: https://phabricator.apertis.org/D4340