Fix the grammar of nfs-down alert

alerts/nfs-down.rules

@@ -4,7 +4,7 @@ ALERT GitNFSServerDown
   LABELS {severity="critical", pager="pagerduty"}
   ANNOTATIONS {
     title="Git NFS Server {{$labels.instance}} is down",
-    description="One of git NFS servers is down, this locks the whole application and causes downtime",
+    description="One git NFS server is down, this locks the whole application and causes downtime",
     runbook="troubleshooting/nfs-server.md"
   }
@@ -14,6 +14,6 @@ ALERT FileNFSServerDown
   LABELS {severity="critical", pager="pagerduty"}
   ANNOTATIONS {
     title="File NFS Server {{$labels.instance}} is down",
-    description="File NFS server is down, this locks the whole application and causes downtime",
+    description="One file NFS server is down, this locks the whole application and causes downtime",
     runbook="troubleshooting/nfs-server.md"
   }