`@test_throws` added features in v1.8 that are not listed under compat in docstring

The ability to write a string `@test_throws "expected message" expr` [was not present in julia v1.6](https://github.com/JuliaLang/julia/blob/v1.6.0/stdlib/Test/src/Test.jl#L575) or 1.7, but is not listed under compat in julia v1.8