[Swift] fix(#18074): correctly map OpenAPIDateWithoutTime to string in path (#18077)

samples/client/petstore/swift5/asyncAwaitLibrary/PetstoreClient/Classes/OpenAPIs/APIHelper.swift

@@ -61,6 +61,8 @@ public struct APIHelper {
             return collection
                 .compactMap { value in convertAnyToString(value) }
                 .joined(separator: ",")
+        } else if let value = source as? any RawRepresentable {
+            return "\(value.rawValue)"
         }
         return source
     }