also fix mst test for tilde in rkeys

the tilde is before the hyphen (different order from the spec) to avoid the hyphen being treated as a regex range

mst/mst_test.go

···
 	for i := 0; i < 256; i++ {
 		f.Add([]byte{byte(i)})
 	}
-	rx := regexp.MustCompile("^[a-zA-Z0-9_:.-]+$")
+	rx := regexp.MustCompile("^[a-zA-Z0-9_:.~-]+$")
 	f.Fuzz(func(t *testing.T, in []byte) {
 		s := string(in)
 		if a, b := rx.MatchString(s), keyHasAllValidChars(s); a != b {