Small update to be correlated with our DOC

https://www.percona.com/doc/percona-monitoring-and-management/conf-mysql.html#pmm-conf-mysql-user-account-creating

Author: rnovikovP

README.md

@@ -9,7 +9,7 @@ NOTE: Not all collection methods are supported on MySQL < 5.6
 ### Required Grants
 
 ```sql
-CREATE USER 'exporter'@'localhost' IDENTIFIED BY 'XXXXXXXX' WITH MAX_USER_CONNECTIONS 3;
+CREATE USER 'exporter'@'localhost' IDENTIFIED BY 'XXXXXXXX' WITH MAX_USER_CONNECTIONS 10;
 GRANT PROCESS, REPLICATION CLIENT, SELECT ON *.* TO 'exporter'@'localhost';
 ```