Revert "boards: mps3_corstone300_fvp_ns: disable twister"

What is changed?
 - This reverts commit 1c596b8b.

Why is this change needed?
 - This commit was added as a temporary fix for #81656.
   Since the previous commit (part of #83360) fixes the issue,
   we don't need this anymore.

Signed-off-by: Sudan Landge <sudan.landge@arm.com>