Update monitor-troubleshoot.rst

added missing letter in grep

docs/source/troubleshooting/monitor-troubleshoot.rst

@@ -166,7 +166,7 @@ Prometheus fails to fetch metrics from ``node_exporter``.
 Solution
 .........
 
-1. Make sure that ``node_exporter`` is running on each Scylla server (by login to the machine and running ``ps -ef |gre node_exporter``). ``node_exporter`` is installed with ``scylla_setup``.
+1. Make sure that ``node_exporter`` is running on each Scylla server (by login to the machine and running ``ps -ef | grep node_exporter``). ``node_exporter`` is installed with ``scylla_setup``.
 to check that ``node_exporter`` is installed, run ``node_exporter --version``, If it is not, make sure to install and run it.
 
 2. If it is running, use ``curl http://<scylla_node>:9100/metrics`` (where <scylla_node> is a Scylla server IP) to fetch metric data from the ``node_exporter``.  If curl does not return data, the problem is the connectivity between Scylla Monitoring Stack and Scylla server. Please check your IPs and firewalls.