Fix broken test

Author: JoshMock

test/unit/client.test.ts

@@ -461,7 +461,7 @@ test('user agent is in the correct format', t => {
   const client = new Client({ node: 'http://localhost:9200' })
   const agentRaw = client.transport[symbols.kHeaders]['user-agent'] || ''
   const agentSplit = agentRaw.split(/\s+/)
-  t.equal(agentSplit[0].split('/')[0], 'elasticsearch-js')
+  t.equal(agentSplit[0].split('/')[0], 'elasticsearch-serverless-js')
   t.ok(/^\d+\.\d+\.\d+/.test(agentSplit[0].split('/')[1]))
   t.end()
 })