avoid uppercasing identifiers

[kzidane]

There is a bug in sqlparse where passing keyword_case="upper" to sqlparse.format causes it to uppercase any instances of keyword, even when used as an identifier rather than a keyword. For example:

SELECT 1 AS count;

would end up executing:

SELECT 1 AS COUNT;

This PR removes keyword_case for now.

[dmalan]

Is that a known bug in their repo? Or should we open?

[kzidane]

I think andialbrecht/sqlparse#611 references the same behavior.