Description of the issue
Once the user selects the VPC from the machine pool step in ROSA Hypershift wizard flow , automatically three machine pool options are shown and listed with subnet drop-down.
It seems wrong user experience behavior as it is not mandatory to have three machine pool /worker nodes for HCP. I would suggest to keep the only one machine pool option with subnet drop-down by default. This helps to avoid confusion and user could go on with n number of machine pools by using add machine pool option.

Steps to Reproduce:

1. Launch OCM UI staging.
2. Create a multi-zone ROSA classic cluster with custom VPC option (Make sure you have three AZs definition selected i.e. subnets)  via ROSA wizard.
3. After cluster submission, Open ROSA wizard
4. Choose control plane type as "Hosted".
5. Reach to "Machine pool" step
6. Select the VPC.
7. See the machine pool options and its behavior

Actual results:

At Step 6, There are three machine pool set added to the UI and it looks a confusing behavior. For example, the selected VPC has only one private subnet (which is minimum requirement for the HCP cluster) and representing three machine pool option would confuse and user has to manually remove those definition from UI.

Expected results:

Keep only one machine pool option by default from machine pool step of ROSA HCP wizard during the selection of a VPC. If additional machine pools are required user could go on by adding to the list using add machine pool. 
ex: