README: fix compilation warning in example

Author: nim65s

README.md

@@ -62,7 +62,7 @@ For an example with using Serde deserialization, please refer to [serde_integrat
 
 
 ```rust
-use influxdb::{Client, Query, Timestamp, ReadQuery};
+use influxdb::{Client, Timestamp, ReadQuery};
 use influxdb::InfluxDbWriteable;
 use chrono::{DateTime, Utc};