Update Minimum terraform version in Makefile from 1.2 to 1.5.7

[RachaelSTamakloe]

This PR updates the MIN_TERRAFORM_VERSION in Makefile from v1.2 to v1.5.7 as documented here.

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[tpdownes]

I observe the proper warning after installing Terraform 1.5.6 and Terraform 1.2.0:

~/cluster-toolkit (min_terraform_version)❯❯❯ make && make install
Makefile:153: WARNING: terraform version must be greater than 1.5.7 , update at https://learn.hashicorp.com/tutorials/terraform/install-cli

I do not observe this on latest (1.10.4) or 1.5.7.