[trusty] Remove unused FallibleVec import am: da3059dc65

Original change: https://android-review.googlesource.com/c/trusty/app/keymint/+/2843978

Change-Id: I26fc3716d409e12de755e224a13dddfc628e6bbc
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>