Error message on Len() assumes string

[kevinburkesegment]

This error message in assert.Len assumes that whatever you are asserting a length about can be formatted with the %s format string.

	if l != length {
		return Fail(t, fmt.Sprintf("\"%s\" should have %d item(s), but has %d", object, length, l), msgAndArgs...)
	}

If you look at the failure in e.g. https://drone.grafana.net/grafana/dskit/3189/1/4, I believe this is a []uint32, which is being formatted as "[%!s(uint32=2452015680) %!s(uint32=2476020736)]".

I think the %v format string might be a better fit.

[dolmen]

@kevinburkesegment Could you submit a patch?

If you submit an MR I will be able to merge it.
However if I do the MR myself I will not be able to merge it because, despites being a maintainer, I need another maintainer to validate it, but all other maintainers are not responsive.

[dolmen]

Reproducer: https://go.dev/play/p/xH-RSrn8HP6

func Test(t *testing.T) {
	assert.Len(t, [...]int{1, 2, 3}, 1)
}

=== RUN   Test
    prog_test.go:10: 
        	Error Trace:	/tmp/sandbox2682030218/prog_test.go:10
        	Error:      	"[%!s(int=1) %!s(int=2) %!s(int=3)]" should have 1 item(s), but has 3
        	Test:       	Test
--- FAIL: Test (0.00s)
FAIL