Should not require parallel tests if `T.Setenv()` is called

[gdavison]

According to the documentation for T.Setenv(), B.Setenv(), and F.Setenv()

Because Setenv affects the whole process, it cannot be used in parallel tests or tests with parallel ancestors.

Calls to Setenv will panic if called in a parallel test

The tparallel linter should not require parallel tests if Setenv is called in the function