The license file is not well referenced
The license name should be MIT. Instead, the name of the license is the whole license. This is a problem for our license checker.
Typically, license files are named simply "LICENSE." Please let me know if that's what you meant or if I misunderstood your point.
Per the license section of the project.toml docs:
The new format for license is a valid SPDX license expression consisting of one or more license identifiers. The full license list is available at the SPDX license list page. The supported list version is 3.17 or any later compatible one.
To use a file reference, I believe all you need is to instead use license-files:
license-files = ["LICEN[CS]E*", "vendored/licenses/*.txt", "AUTHORS.md"]
Though from the look of the existing license, this seems a simple MIT. Maybe it's safe to drop it and simply use one of the well known variants in string version: