DOCS-14284 fix start snmpd step Linux

Author: andf-mongodb

source/includes/steps-monitor-with-snmp.yaml

@@ -172,13 +172,13 @@ content: |
 
     .. code-block:: sh
 
-       sudo systemctl start mongod
+       sudo systemctl start snmpd
 
   - For Linux systems using **System V init** (``service`` command):
 
     .. code-block:: sh
 
-       sudo service mongod start
+       sudo service snmpd start
 ---
 title: Start MongoDB.
 stepnum: 4