Format of concat ||

**Problem**
Mo-sql-parsing parses the concat operator, ||, as:
```py
query_parser(""" select 'a' || 'a' """)
>> {'select': {'value': {'concat': {'literal': ['a', 'a']}}}}
```
And format as:
```py
format({'select': {'value': {'concat': {'literal': ['a', 'a']}}}})    
>> "SELECT literal || ('a', 'a')"
```