Use heck-0.3.3 am: 960abda7c6 am: 8d4f507515

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/structopt-derive/+/2209805

Change-Id: I7df31f5d334ce0c64bb8589b56a164661b90cea2
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>