Bump firewall-github-runners::cloud-foundation-fabric in /gcp

Bumps [firewall-github-runners::cloud-foundation-fabric](https://github.com/GoogleCloudPlatform/cloud-foundation-fabric) from 49.1.0 to 51.0.0.
- [Release notes](https://github.com/GoogleCloudPlatform/cloud-foundation-fabric/releases)
- [Changelog](https://github.com/GoogleCloudPlatform/cloud-foundation-fabric/blob/master/CHANGELOG.md)
- [Commits](GoogleCloudPlatform/cloud-foundation-fabric@v49.1.0...v51.0.0)

---
updated-dependencies:
- dependency-name: firewall-github-runners::github::GoogleCloudPlatform/cloud-foundation-fabric::v49.1.0
  dependency-version: 51.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

gcp/net-vpc.tf

@@ -18,7 +18,7 @@ module "vpc-github-runners" {
 # Firewall rules for GitHub Actions Runners
 # https://github.com/GoogleCloudPlatform/cloud-foundation-fabric/tree/v49.1.0/modules/net-vpc-firewall
 module "firewall-github-runners" {
-  source               = "git::https://github.com/GoogleCloudPlatform/cloud-foundation-fabric//modules/net-vpc-firewall?ref=v49.1.0"
+  source               = "git::https://github.com/GoogleCloudPlatform/cloud-foundation-fabric//modules/net-vpc-firewall?ref=v51.0.0"
   project_id           = module.project.project_id
   network              = module.vpc-github-runners.name
   default_rules_config = { disabled = true }