Migrate to newer `hashicorp/null` provider

[joshgarde]

The version constraint on the hashicorp/null provider is preventing deployments on macOS ARM-architecture machines as there's no ARM builds for the specified version constraint. Should be bumped and made less strict

tig/terraform/main.tf

Lines 16 to 19 in d08f5f9

	null = {
	source = "hashicorp/null"
	version = "~> 2.1"
	}