Fix httpClient initialization, assign it to class field instead of local variable.

Author: Szychulski

trino-csharp/Trino.Client/StatementClientV1.cs

@@ -146,7 +146,7 @@ internal StatementClientV1(
                 return sslPolicyErrors == SslPolicyErrors.None;
             };
 
-            HttpClient httpClient = new HttpClient(handler);
+            this.httpClient = new HttpClient(handler);
             this.httpClient.Timeout = Constants.HttpConnectionTimeout;
 
             if (!this.Session.Properties.CompressionDisabled)