Remove parallel runs for vertex_endpoint_iam tests (#12009) (#8419)

[upstream:3108f691db6404ed1d3afa0672f48916115579e6]

Signed-off-by: Modular Magician <[email protected]>

Author: modular-magician

.changelog/12009.txt

@@ -0,0 +1,3 @@
+```release-note:none
+
+```

google-beta/services/vertexai/iam_vertex_endpoint_test.go

@@ -13,7 +13,8 @@ import (
 )
 
 func TestAccVertexAIEndpointIamBinding(t *testing.T) {
-	t.Parallel()
+	// t.Parallel()
+	// See https://github.com/hashicorp/terraform-provider-google/issues/18932
 
 	context := map[string]interface{}{
 		"random_suffix": acctest.RandString(t, 10),
@@ -48,7 +49,7 @@ func TestAccVertexAIEndpointIamBinding(t *testing.T) {
 }
 
 func TestAccVertexAIEndpointIamMember(t *testing.T) {
-	t.Parallel()
+	// t.Parallel()
 
 	context := map[string]interface{}{
 		"random_suffix": acctest.RandString(t, 10),
@@ -74,7 +75,7 @@ func TestAccVertexAIEndpointIamMember(t *testing.T) {
 }
 
 func TestAccVertexAIEndpointIamPolicy(t *testing.T) {
-	t.Parallel()
+	// t.Parallel()
 
 	context := map[string]interface{}{
 		"random_suffix": acctest.RandString(t, 10),