Fix: Do not double quote TF >= 0.12 legacy quoted types

[cytopia]

Do not double quote TF >= 0.12 legacy quoted types

This PR addresses another issue with double-double quoting legacy types. This happens if you still double quote string, list and map in Terraform >= 0.12.

Error: Invalid legacy variable type hint

  on variables.tf line 2, in variable "test":
   2:   type        = "map(string)"

The legacy variable type hint form, using a quoted string, allows only the
values "string", "list", and "map". To provide a full type expression, remove
the surrounding quotes and give the type expression directly.

You can find the reporting here: antonbabenko/pre-commit-terraform#52 (comment)

As well as the initial fix including regression tests here: cytopia/docker-terraform-docs#16

An example to reproduce the faulty behaviour (before this PR might be merged) can be found here:
https://github.com/cytopia/docker-terraform-docs/blob/master/tests/0.12/main.tf#L60

[aknysh]

thanks @cytopia