`cwltool --pack` generates IDs for enum symbols

When I pack a conformance test that contains an enum type (e.g. https://github.com/common-workflow-language/cwl-v1.2/blob/main/tests/anon_enum_inside_array.cwl) the packed workflow turns the enum symbols into URI fragments. The symbols should not be modified.

```
{
"class": "CommandLineTool",
"inputs": [
{
"type": {
"type": "record",
"fields": [
{
"type": [
{
"type": "enum",
"symbols": [
"#main/first/species/homo_sapiens",
"#main/first/species/mus_musculus"
]
},
"null"
],
"name": "#main/first/species"
}
]
},
"id": "#main/first"
},
{
"type": [
"null",
{
"type": "enum",
"symbols": [
"#main/second/homo_sapiens",
"#main/second/mus_musculus"
]
}
],
"id": "#main/second"
}
],
"baseCommand": "echo",
"arguments": [
{
"prefix": "first",
"valueFrom": "$(inputs.first.species)"
},
{
"prefix": "second",
"valueFrom": "$(inputs.second)"
}
],
"outputs": [
{
"type": "File",
"id": "#main/result",
"outputBinding": {
"glob": "4114671e652492b7e2f05b10178342c11c66195b"
}
}
],
"id": "#main",
"stdout": "4114671e652492b7e2f05b10178342c11c66195b",
"cwlVersion": "v1.2"
}
```