Update link to the poco logging levels

dbms/programs/server/config.xml

@@ -23,7 +23,7 @@
 	</remote_url_allow_hosts>
 
     <logger>
-        <!-- Possible levels: https://github.com/pocoproject/poco/blob/develop/Foundation/include/Poco/Logger.h#L105 -->
+        <!-- Possible levels: https://github.com/pocoproject/poco/blob/poco-1.9.4-release/Foundation/include/Poco/Logger.h#L105 -->
         <level>trace</level>
         <log>/var/log/clickhouse-server/clickhouse-server.log</log>
         <errorlog>/var/log/clickhouse-server/clickhouse-server.err.log</errorlog>