fix test fixture had the instance in the wrong mod

Make the state match the fixture config. The old test was not
technically invalid, but because it caused multiple instances of the
provider to be created, they were backed by the same MockProvider value
resulting in the `*Called` fields interfering.

internal/terraform/context_apply_test.go

@@ -1543,8 +1543,8 @@ func TestContext2Apply_destroyModuleVarProviderConfig(t *testing.T) {
 	p := testProvider("aws")
 	p.PlanResourceChangeFn = testDiffFn
 	state := states.NewState()
-	root := state.EnsureModule(addrs.RootModuleInstance)
-	root.SetResourceInstanceCurrent(
+	child := state.EnsureModule(addrs.RootModuleInstance.Child("child", addrs.NoKey))
+	child.SetResourceInstanceCurrent(
 		mustResourceInstanceAddr("aws_instance.foo").Resource,
 		&states.ResourceInstanceObjectSrc{
 			Status:    states.ObjectReady,