resource/aws_redshift_cluster: Increase default Update timeout to 75 …

…minutes and remove arbitrary lower create timeout in testing

Reference: #14754

Previously (inconsistently):

```
=== CONT  TestAccAWSRedshiftCluster_basic
TestAccAWSRedshiftCluster_basic: resource_aws_redshift_cluster_test.go:69: Step 1/2 error: terraform failed: exit status 1
stderr:
Error: Error waiting for Redshift Cluster state to be "available": timeout while waiting for state to become 'available' (last state: 'creating', timeout: 30m0s)

=== CONT  TestAccAWSRedshiftCluster_changeEncryption1
TestAccAWSRedshiftCluster_changeEncryption1: resource_aws_redshift_cluster_test.go:526: Step 1/2 error: terraform failed: exit status 1
stderr:
Error: Error waiting for Redshift Cluster state to be "available": timeout while waiting for state to become 'available' (last state: 'creating', timeout: 30m0s)

=== CONT  TestAccAWSRedshiftCluster_updateNodeCount
TestAccAWSRedshiftCluster_updateNodeCount: resource_aws_redshift_cluster_test.go:353: Step 1/2 error: terraform failed: exit status 1
stderr:
Error: Error waiting for Redshift Cluster state to be "available": timeout while waiting for state to become 'available' (last state: 'creating', timeout: 30m0s)

=== CONT  TestAccAWSRedshiftCluster_updateNodeType
TestAccAWSRedshiftCluster_updateNodeType: resource_aws_redshift_cluster_test.go:390: Step 1/2 error: terraform failed: exit status 1
stderr:
Error: Error waiting for Redshift Cluster state to be "available": timeout while waiting for state to become 'available' (last state: 'creating', timeout: 30m0s)

=== CONT  TestAccAWSRedshiftCluster_updateNodeCount
TestAccAWSRedshiftCluster_updateNodeCount: resource_aws_redshift_cluster_test.go:353: Step 2/2 error: terraform failed: exit status 1
stderr:
Error: Error Modifying Redshift Cluster (tf-redshift-cluster-7778138192916979662): timeout while waiting for state to become 'available' (last state: 'resizing', timeout: 40m0s)
```

The 75 minute update timeout value is chosen to match the create timeout value.

Output from acceptance testing:

```
... pending ...
```

aws/resource_aws_redshift_cluster.go

@@ -28,7 +28,7 @@ func resourceAwsRedshiftCluster() *schema.Resource {
 
 		Timeouts: &schema.ResourceTimeout{
 			Create: schema.DefaultTimeout(75 * time.Minute),
-			Update: schema.DefaultTimeout(40 * time.Minute),
+			Update: schema.DefaultTimeout(75 * time.Minute),
 			Delete: schema.DefaultTimeout(40 * time.Minute),
 		},
 

aws/resource_aws_redshift_cluster_test.go

@@ -765,10 +765,6 @@ resource "aws_redshift_cluster" "default" {
   automated_snapshot_retention_period = 0
   allow_version_upgrade               = false
   skip_final_snapshot                 = true
-
-  timeouts {
-    create = "30m"
-  }
 }
 `, rInt))
 }

website/docs/r/redshift_cluster.html.markdown

@@ -79,7 +79,7 @@ string.
 [Timeouts](/docs/configuration/resources.html#timeouts) configuration options:
 
 - `create` - (Default `75 minutes`) Used for creating Clusters.
-- `update` - (Default `40 minutes`) Used for Cluster Argument changes.
+- `update` - (Default `75 minutes`) Used for updating Clusters.
 - `delete` - (Default `40 minutes`) Used for destroying Clusters.
 
 ### Nested Blocks