[monitor-query] fix build error (Azure#21550)

The test is checking a private property of ServiceClient that just got renamed.

This PR fixes the build. Another issue will be logged to improve the test by
testing that the option is passed to ServiceClient via a mock, instead of
verifying the internals of ServiceClient

Author: jeremymeng

sdk/monitor/monitor-query/test/internal/unit/logsQueryClient.unittest.spec.ts

@@ -33,7 +33,7 @@ describe("LogsQueryClient unit tests", () => {
     });
 
     assert.equal(client["_logAnalytics"].$host, "https://customEndpoint1");
-    assert.equal(client["_logAnalytics"]["_baseUri"], "https://customEndpoint1");
+    assert.equal(client["_logAnalytics"]["_endpoint"], "https://customEndpoint1");
 
     try {
       await client.queryWorkspace("workspaceId", "query", { duration: Durations.fiveMinutes });