[SPARK-33818][SQL][DOC] Add descriptions about `spark.sql.parser.quot…

…edRegexColumnNames` in the SQL documents

### What changes were proposed in this pull request?
According to apache#30805 (comment),
doc `spark.sql.parser.quotedRegexColumnNames` since  we need user know about this in doc and it's useful.

![image](https://user-images.githubusercontent.com/46485123/103656543-afa4aa80-4fa3-11eb-8cd3-a9d1b87a3489.png)
![image](https://user-images.githubusercontent.com/46485123/103656551-b2070480-4fa3-11eb-9ce7-95cc424242a6.png)

### Why are the changes needed?
Complete doc

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?
Not need

Closes apache#30816 from AngersZhuuuu/SPARK-33818.

Authored-by: angerszhu <angers.zhu@gmail.com>
Signed-off-by: Dongjoon Hyun <dhyun@apple.com>

docs/sql-ref-syntax-qry-select.md

@@ -41,7 +41,7 @@ select_statement [ { UNION | INTERSECT | EXCEPT } [ ALL | DISTINCT ] select_stat
 
 While `select_statement` is defined as
 ```sql
-SELECT [ hints , ... ] [ ALL | DISTINCT ] { [ [ named_expression | regex_column_names ] [ , ... ] | TRANSFORM (...) ] }
+SELECT [ hints , ... ] [ ALL | DISTINCT ] { [ named_expression | regex_column_names ] [ , ... ] }
     FROM { from_item [ , ... ] }
     [ PIVOT clause ]
     [ LATERAL VIEW clause ] [ ... ] 
@@ -164,10 +164,6 @@ SELECT [ hints , ... ] [ ALL | DISTINCT ] { [ [ named_expression | regex_column_
      )
      ```
 
-* **TRANSFORM**
-
-     Specifies a hive-style transform query specification to transform the input by forking and running user-specified command or script.
-
 ### Related Statements
 
 * [WHERE Clause](sql-ref-syntax-qry-select-where.html)