Set required Terraform version for examples

Author: aaron-lane

examples/mysql-ha/versions.tf

@@ -15,5 +15,5 @@
  */
 
 terraform {
-  required_version = "~> 0.12.0"
+  required_version = "~> 0.12.6"
 }

examples/mysql-private/versions.tf

@@ -15,5 +15,5 @@
  */
 
 terraform {
-  required_version = ">= 0.12"
+  required_version = "~> 0.12.6"
 }

examples/postgresql-ha/versions.tf

@@ -15,6 +15,6 @@
  */
 
 terraform {
-  required_version = "~> 0.12.0"
+  required_version = "~> 0.12.6"
 }