[CHORE] ignore wit deps

[ricochet]

With the wkg.lock files in place, the deps can be regenerated by running wash wit fetch which also happens automatically with a wash build.

• Add wit/deps/ to .gitignore
• Remove the currently tracked wit/deps/ files from git

The awkwardness is for projects like wash itself that uses cargo to build and not wash build (so no automatic wit fetch). So we need to add this to build.rs.