fix: prometheus shouldnt use latest (#924)

Prometheus for some reason overrides their bugfix releases for older
versions of major prom versions with `latest`, breaking everything for
everyone else.

src/package_io/input_parser.star

@@ -1169,7 +1169,7 @@ def get_default_prometheus_params():
         "max_cpu": 1000,
         "min_mem": 128,
         "max_mem": 2048,
-        "image": "prom/prometheus:latest",
+        "image": "prom/prometheus:v3.2.1",
     }