update comments

main.tf

@@ -1,12 +1,12 @@
 /**
  * Usage:
 * 
-* for terraform 0.11, use v1.0.0 (tf-0.11)
-* for terraform 0.12, use v2.0.0 (or later), or branch tf-upgrade-0.12 (tf-0.12)
+* for terraform 0.11 v1.x use tf-0.11
+* for terraform 0.12 v2.x use tf-0.12 (until rolled into head) or specific version v2.x.y
 *
 * module "scanner" {
 *   source = "../module/aws-security-audit"
-*   source = "git::https://vc1.csvd.census.gov/terraform-modules/aws-security-audit.git?ref=tf-upgrade-0.12
+*   source = "git::https://vc1.csvd.census.gov/terraform-modules/aws-security-audit.git?ref=tf-0.12
 * 
 *   group = "g-audit-group"
 *   users = [ "s-ois-scan" ]