[bug](jdbc) fix jdbc external table with char type length error (#15386)

Now have test pg and oracle with char(100), if data='abc'
but read string data length is 100, so need trim extral spaces

fe/fe-core/src/main/java/org/apache/doris/planner/JdbcScanNode.java

@@ -195,6 +195,7 @@ public class JdbcScanNode extends ScanNode {
         msg.jdbc_scan_node.setTupleId(desc.getId().asInt());
         msg.jdbc_scan_node.setTableName(tableName);
         msg.jdbc_scan_node.setQueryString(getJdbcQueryStr());
+        msg.jdbc_scan_node.setTableType(jdbcType);
     }
 
     @Override