chore(gitignore): ignore dependency lockfile

Terraform 0.14's new dependency lock file,
focused on providers, simplifies managing
Terraform automation. Starting in Terraform 0.13,
the possibility of installing providers from
customer-controlled or third-party remote
registries increases the need to be able to
replicate Terraform runs in automation.
These remote and automated Terraform workflows
need to be able to duplicate previous runs exactly.

This commit add .terraform.lock.hcl exclusion
in gitignore.

.gitignore

@@ -1,9 +1,10 @@
 .terraform
+.terraform.lock.hcl
 *.tfstate*
 *.zip
 terraform.tfstate.d
 .tox
 __pycache__
 .pytest_cache
 .coverage
-.mypy_cache
+.mypy_cache