Delete a schema definition
Examples
schema <- schema_doc(schema_check("string"))
schema <- schema_add_def(schema, "text", schema_check("string"))
schema <- schema_del_def(schema, "text")
schema
#> {
#> "check": {
#> "kind": "string"
#> }
#> }
as.list(schema)$`$defs`
#> NULL