Mark "check valid item" test as required

This has passed for years now, no reason for it to be optional.

projects/common/src/testMod/kotlin/dan200/computercraft/gametest/Inventory_Test.kt

@@ -24,7 +24,7 @@ class Inventory_Test {
      *
      * @see <https://github.com/cc-tweaked/cc-restitched/issues/121>
      */
-    @GameTest(required = false)
+    @GameTest
     fun Checks_valid_item(helper: GameTestHelper) = helper.sequence {
         thenOnComputer {
             getApi<PeripheralAPI>().call(