`license-file` key in Cargo manifest is not read for path dependencies in a workspace

**Describe the bug**
Path dependencies that specify a `license-file` get the generic MIT license text.

**To Reproduce**
Run `cargo about` with Artichoke as of this PR: https://github.com/artichoke/artichoke/pull/1420.

**Expected behavior**
Path dependencies in the current workspace use the given license file.

**Screenshots**
If applicable, add screenshots to help explain your problem.

Reproduce the issue by running cargo about with the Artichoke example from PR 1420, then trace how license metadata is resolved for path dependencies in the current workspace. Done means a path dependency's specified license-file is used instead of the generic MIT license text.

Written by the indexing model from the issue text.