fix missing import

Author: KrumTy

redisinsight/ui/src/components/monitor/MonitorHeader/MonitorHeader.tsx

@@ -1,5 +1,6 @@
 import React from 'react'
 import { useDispatch, useSelector } from 'react-redux'
+import cx from 'classnames'
 import { useParams } from 'react-router-dom'
 import { EuiIcon } from '@elastic/eui'