ipynb: testenv: update example to use a single configuration fragment
ipynb: testenv: update example to use a single configuration fragment

When we use the TestEnv module we usually use just the API create custom
experiments, i.e. not an experiments set defined using the Executor.
This patch simplify the example by using just the target configuration to
setup all the parameters required to access the target.

Signed-off-by: Patrick Bellasi <431c86f368affbc3148c4669fbd465131f7e82cb@arm.com>

mdigiorgio/lisa,credp/lisa,bjackman/lisa,credp/lisa,bjackman/lisa,credp/lisa,mdigiorgio/lisa,joelagnel/lisa,ARM-software/lisa,arnoldlu/lisa,arnoldlu/lisa,joelagnel/lisa,ARM-software/lisa,ARM-software/lisa,credp/lisa,JaviMerino/lisa,ARM-software/lisa