Fix typo in comment of match_orclause_to_indexcol()

Hi,

While debugging the optimizer codes, I found a typo
in match_orclause_to_indexcol():

/*
* Try to convert a list of OR-clauses to a single SAOP expression. Each
* OR entry must be in the form: (indexkey operator constant) or (constant
* operator indexkey).  Operators of all the entries must match.  To be
* effective, give up on the first non-matching entry.  Exit is
* implemented as a break from the loop, which is catched afterwards.
*/

"catched" should be "caught".

The attached patch fixes it.

-- 
Thanks,
Tender Wang