Fix name for blackbox-exporter PodSecurityPolicy

jsonnet/kube-prometheus/addons/podsecuritypolicies.libsonnet

@@ -117,7 +117,11 @@ local restrictedPodSecurityPolicy = {
             },
           }
         else
-          {};
+          {
+            metadata+: {
+              name: 'blackbox-exporter-psp',
+            },
+          };
 
       restrictedPodSecurityPolicy + blackboxExporterPspPrivileged,
   },