refactor: replace SimpleDataClass with Pair for jsr variable test

Author: angelacorte

alchemist-loading/src/test/kotlin/it/unibo/alchemist/test/TestKtVariable.kt

@@ -89,5 +89,3 @@ class TestKtVariable<T, P : Position<P>> :
             loader.variables["simple"] shouldNot beNull()
         }
     })
-
-data class SimpleDataClass(val number: Int, val name: String)

alchemist-loading/src/test/resources/regression/testJSRVariable.yml

@@ -6,5 +6,4 @@ variables:
   simple: &simple
     language: kotlin
     formula: |
-      import it.unibo.alchemist.test.SimpleDataClass
-      val simpleDataClass = SimpleDataClass(number, name)
+      val couple: Pair<Int, String> = number to name