potential bug in input validation

[a-frantz]

I was working on a new sprocket validate-inputs subcommand (WIP here) modeled after this code: https://github.com/stjude-rust-labs/wdl/blob/main/wdl-engine/tests/inputs.rs

The bug could be on my end, but I don't think so.

$ cargo run -- validate-inputs -i ../workflows/workflows/reference/inputs/qc-reference-inputs.json ../workflows/workflows/reference/qc-reference.wdl
   Compiling sprocket v0.9.0 (/Users/afrantz/sprocket)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 3.76s
     Running `target/debug/sprocket validate-inputs -i ../workflows/workflows/reference/inputs/qc-reference-inputs.json ../workflows/workflows/reference/qc-reference.wdl`
error: failed to validate inputs:
failed to validate inputs for workflow `qc_reference`

Caused by:
    missing required input `tarballs`

the referenced files are on main of the workflows repo here and here

Notably, tarballs is not a workflow input. It is an input to a call, but that is explicitly provided by the call here