tests/resource/aws_instance: Correct 'TestAccAWSInstance_EbsRootDevic…

…e_ModifyType'. (#16702)

Acceptance test output:

$ make testacc TEST=./aws/ TESTARGS='-run=TestAccAWSInstance_EbsRootDevice_ModifyType'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./aws -v -count 1 -parallel 20 -run=TestAccAWSInstance_EbsRootDevice_ModifyType -timeout 120m
=== RUN   TestAccAWSInstance_EbsRootDevice_ModifyType
=== PAUSE TestAccAWSInstance_EbsRootDevice_ModifyType
=== CONT  TestAccAWSInstance_EbsRootDevice_ModifyType
--- PASS: TestAccAWSInstance_EbsRootDevice_ModifyType (126.02s)
PASS
ok  	github.com/terraform-providers/terraform-provider-aws/aws	126.110s

aws/resource_aws_instance_test.go

@@ -1540,7 +1540,7 @@ func TestAccAWSInstance_EbsRootDevice_ModifyType(t *testing.T) {
 	deleteOnTermination := "true"
 
 	originalType := "gp2"
-	updatedType := "io1"
+	updatedType := "standard"
 
 	resource.ParallelTest(t, resource.TestCase{
 		PreCheck:     func() { testAccPreCheck(t) },