chore: enable test shuffle and fix test

[alexandear]

This PR extends go test with -shuffle flag and fixes failing TestXDGConfigDirNoFile:

--- FAIL: TestXDGConfigDirNoFile (0.00s)
    main_test.go:80: got "", wanted "/tmp-iofs/xdg/config/revive.toml"
FAIL

The shuffle flag description from https://pkg.go.dev/cmd/go#hdr-Testing_flags:

-shuffle off,on,N
    Randomize the execution order of tests and benchmarks.
    It is off by default. If -shuffle is set to on, then it will seed
    the randomizer using the system clock. If -shuffle is set to an
    integer N, then N will be used as the seed value. In both cases,
    the seed will be reported for reproducibility.

[alexandear]

Lint issue fixed by #1096