docs - describe pxf jdbc profile QUOTE_COLUMNS option (#7204)

* docs - describe pxf jdbc profile QUOTE_COLUMNS option

* clarify per comment from ivan

gpdb-doc/markdown/pxf/jdbc_pxf.html.md.erb

@@ -98,6 +98,7 @@ The `Jdbc` profile supports the following \<custom-option\> values:
 | PARTITION_BY | Read | The partition column, \<column-name\>:\<column-type\>. You may specify only one partition column. The JDBC connector supports `date`, `int`, and `enum` \<column-type\> values. A null `PARTITION_BY` defaults to a single fragment. |
 | RANGE | Read | Required when `PARTITION_BY` is specified. The query range, \<start-value\>[:\<end-value\>]. When the partition column is an `enum` type, `RANGE` must specify a list of values, each of which forms its own fragment. If the partition column is an `int` or `date` type, `RANGE` must specify a finite left-closed range. That is, the range includes the \<start-value\> but does *not* include the \<end-value\>. If the partition column is a `date` type, use the `yyyy-MM-dd` date format. |
 | INTERVAL | Read | Required when `PARTITION_BY` is specified and of the `int` or `date` type. The interval, \<interval-value\>[:\<interval-unit\>], of one fragment. Specify the size of the fragment in \<interval-value\>. If the partition column is a `date` type, use the \<interval-unit\> to specify `year`, `month`, or `day`. |
+| QUOTE_COLUMNS | Read | Controls whether PXF should quote column names when constructing an SQL query to the external database. Specify `true` to force PXF to quote all column names; PXF does not quote column names if any other value is provided. If `QUOTE_COLUMNS` is not specified (the default), PXF automatically quotes *all* column names in the query when *any* column name:<br>- includes special characters, or <br>- is mixed case and the external database does not support unquoted mixed case identifiers. |
 
 Example JDBC \<custom-option\> connection strings: