Increase amount of CPU cores required in arm macOS templates

All tart hosts are limited to running maximum of 2 VM at a time. In Opennebula we use amount of CPU cores to limit how many VM can be run simultaneously.

Tier 1 tart templates have their CPU cores required currently 2. This introduces a problem when manually starting a VM as it can fit in a M4 host with 2 running VM's and cause a hard to diagnose failure in Opennebula.

Raise amount of CPU cores required to 6 for all Tier 1 templates to reduce the risk of a host attempting to run 3 VM's simultaneously.