Bump relaycorp/awala-gateway/google in /environments/belgium

Bumps [relaycorp/awala-gateway/google](https://github.com/relaycorp/terraform-google-awala-gateway) from 1.6.3 to 1.6.8.
- [Release notes](https://github.com/relaycorp/terraform-google-awala-gateway/releases)
- [Changelog](https://github.com/relaycorp/terraform-google-awala-gateway/blob/main/.releaserc.yml)
- [Commits](relaycorp/terraform-google-awala-gateway@v1.6.3...v1.6.8)

---
updated-dependencies:
- dependency-name: relaycorp/awala-gateway/google
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

environments/_modules/gateway/gateway.tf

@@ -1,6 +1,6 @@
 module "gateway" {
   source  = "relaycorp/awala-gateway/google"
-  version = "1.6.3"
+  version = "1.6.8"
 
   project_id = var.gcp_project_id
   region     = var.gcp_region