configs: Removed redudant exec-style import

configs: Removed redudant exec-style import

garnet_synth_traffic.py imports common.Options on line 40, so exec'ing
the Options.py file again seems redundant.

It also runs Options.py as a script rather than a module, which throws
ValueError: Attempted relative import in non-package due to the recent
change to python3 imports.

Change-Id: Id729a8dfa776af0d14312e765168aff6900eb727
Signed-off-by: Ryan Gambord <gambordr@oregonstate.edu>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17888
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>