Split('a,b', '-') should return a list, but returns a valueString

[bryantaustin13]

cql-tests CqlStringOperatorsTest.xml:: SplitABDash demonstrates the error.

https://cql.hl7.org/09-b-cqlreference.html#split states:
"If the stringToSplit argument does not contain any appearances of the separator, the result is a list of strings containing one element that is the value of the stringToSplit argument."

Split('a,b', '-') returns
"parameter": [
{
"name": "return",
"valueString": "a,b"
}
]
It should return
"parameter": [
{
"name": "return",
"valueString": "{a,b}"
}
]