build(deps): bump prom/alertmanager in /generators/server/resources (#…

…28483)

Bumps prom/alertmanager from v0.27.0 to v0.28.0.

---
updated-dependencies:
- dependency-name: prom/alertmanager
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

generators/server/resources/Dockerfile

@@ -55,7 +55,7 @@ LABEL ALIAS=consul
 FROM prom/prometheus:v3.1.0
 LABEL ALIAS=prometheus
 
-FROM prom/alertmanager:v0.27.0
+FROM prom/alertmanager:v0.28.0
 LABEL ALIAS=prometheus-alertmanager
 
 FROM quay.io/coreos/prometheus-operator:v0.42.1