Use heck-0.3.3 am: 960abda7c6 am: 8d4f507515 am: 5639047125

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

Change-Id: Ibcdce76fa5bc0e9ec83a4a2ac0bf7540ee412d5b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>