Remove deny_warnings attribute am: 06ad3b4d67 am: f378ee9ece am: 4952b54f7a am: 596c423199

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/clap/+/1352861

Change-Id: Ib5e26d14103be2f35584522a0c39326412b2d72b