Fix invalid limit

[nosshar]

https://github.com/jkelly467/kossh/blob/f7d671e241931d73711328588a00382dc12fcdd8/src/main/kotlin/kossh/impl/SSHScp.kt#L93

Kotlin version: 1.4.10

Argument limit=-1 goes to underlying kotlin.text.Regex.split(input: CharSequence, limit: Int = 0) which doesn't accept negative values: require(limit >= 0, { "Limit must be non-negative, but was $limit." })