pgsql: Fix comments in index.c

Fix comments in index.c

This comment paragraph referred to text_eq(), but the name of the
function in charge of "text" comparisons is called texteq().

Author: Jian He <jian.universality@gmail.com>
Discussion: https://postgr.es/m/CACJufxHL--XNcCCO1LgKsygzYGiVHZMfTcAxOSG8+ezxWtjddw@mail.gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/006fc975a2b984249283e953900ac0ee814c5d6b

Modified Files
--------------
src/backend/catalog/index.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)