EKS 1.21 - CFN Template Fixes

Issue #, if available:

Made t2.micro as default for cloud9 as some instances are not available in us-east-1e.
Added 2 AZs in the Create Cluster YAML to avoid us-east-1e randomly getting picked. Also us-west-1 has only 2 AZs.
Removed enableSsm: true, to suppress warning as it's enabled by default.

Description of changes:

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

awslabs / ec2-spot-workshops