hclwrite: do not add space after a bang

[sivapalan]

A space should not be added after a bang (!) - which is used for negation.

See: https://www.terraform.io/docs/configuration/expressions.html#logical-operators

[hashicorp-cla]

All committers have signed the CLA.

[apparentlymart]

Thanks @sivapalan! It does look like the form without a space is what examples show in the Terraform documentation, and that's typically been our guide for what is "idiomatic HCL" given that HCL started its life as a Terraform-specific language.

This unary ! operator doesn't seem to be used often in most Terraform configurations, but I agree it'd be good to make systems built around hclwrite's formatter, such as hclfmt and terraform fmt, match the idiomatic usage nonetheless.

Thanks for working on this!