fix: make http check send a custom user agent

mentioned in commit 05630610

mentioned in issue #1434 (closed)

mentioned in merge request gitlab-org/charts/gitlab!4017 (merged)

mentioned in merge request omnibus-gitlab!8053 (closed)

mentioned in merge request gitlab-org/build/CNG!2111 (merged)

mentioned in merge request gitlab-org/build/CNG!2116 (closed)

mentioned in merge request gitlab-com/gl-infra/k8s-workloads/gitlab-com!4008 (merged)

mentioned in merge request gitlab-com/gl-infra/k8s-workloads/gitlab-com!4009 (merged)

mentioned in merge request gitlab-com/gl-infra/k8s-workloads/gitlab-com!4010 (merged)

mentioned in merge request gitlab-development-kit!4247 (merged)

mentioned in merge request omnibus-gitlab!8073 (merged)