[ATMOSPHERE-521] [stable/2023.2] Remove NodeNonLTSKernel alert (#2048)

This is an automated cherry-pick of #2043
/assign larainema
diff --git a/roles/kube_prometheus_stack/files/jsonnet/legacy.libsonnet b/roles/kube_prometheus_stack/files/jsonnet/legacy.libsonnet
index f250f7e..a3b4dda 100644
--- a/roles/kube_prometheus_stack/files/jsonnet/legacy.libsonnet
+++ b/roles/kube_prometheus_stack/files/jsonnet/legacy.libsonnet
@@ -166,13 +166,6 @@
                 severity: 'P5',
               },
             },
-            {
-              alert: 'NodeNonLTSKernel',
-              expr: 'node_uname_info{release!~"^5.(4|15).*"}',
-              labels: {
-                severity: 'P5',
-              },
-            },
           ],
         },
         {