Bump github.com/hashicorp/terraform-plugin-sdk in /tools

Bumps [github.com/hashicorp/terraform-plugin-sdk](https://github.com/hashicorp/terraform-plugin-sdk) from 1.4.1 to 1.6.0.
- [Release notes](https://github.com/hashicorp/terraform-plugin-sdk/releases)
- [Changelog](https://github.com/hashicorp/terraform-plugin-sdk/blob/master/CHANGELOG.md)
- [Commits](hashicorp/terraform-plugin-sdk@v1.4.1...v1.6.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

tools/go.mod

@@ -4,7 +4,7 @@ go 1.13
 
 require (
 	github.com/hashicorp/hcl/v2 v2.2.0
-	github.com/hashicorp/terraform-plugin-sdk v1.4.1
+	github.com/hashicorp/terraform-plugin-sdk v1.6.0
 	github.com/serenize/snaker v0.0.0-20171204205717-a683aaf2d516
 	github.com/terraform-linters/tflint-plugin-sdk v0.1.0
 	github.com/terraform-providers/terraform-provider-aws v2.43.0+incompatible

tools/go.sum

@@ -239,6 +239,8 @@ github.com/hashicorp/terraform-json v0.3.1/go.mod h1:MdwQStcJb00ht55L/2YH0ypAO9R
 github.com/hashicorp/terraform-plugin-sdk v1.3.0/go.mod h1:fY7uWsWuLHi/hsGmBC2Sm7lic5RlFFjcM4zwua5VDuk=
 github.com/hashicorp/terraform-plugin-sdk v1.4.1 h1:REgN6WbySD6aIYdF6Uob3ic4eQkfh4NXSWU/casmgb4=
 github.com/hashicorp/terraform-plugin-sdk v1.4.1/go.mod h1:H5QLx/uhwfxBZ59Bc5SqT19M4i+fYt7LZjHTpbLZiAg=
+github.com/hashicorp/terraform-plugin-sdk v1.6.0 h1:Um5hsAL7kKsfTHtan8lybY/d03F2bHu4fjRB1H6Ag4U=
+github.com/hashicorp/terraform-plugin-sdk v1.6.0/go.mod h1:H5QLx/uhwfxBZ59Bc5SqT19M4i+fYt7LZjHTpbLZiAg=
 github.com/hashicorp/terraform-svchost v0.0.0-20191011084731-65d371908596 h1:hjyO2JsNZUKT1ym+FAdlBEkGPevazYsmVgIMw7dVELg=
 github.com/hashicorp/terraform-svchost v0.0.0-20191011084731-65d371908596/go.mod h1:kNDNcF7sN4DocDLBkQYz73HGKwN1ANB1blq4lIYLYvg=
 github.com/hashicorp/vault v0.10.4 h1:4x0lHxui/ZRp/B3E0Auv1QNBJpzETqHR2kQD3mHSBJU=