pgsql: Fix oversight in commit 4429f6a9e3e12bb4af6e3677fbc78cd80f160252

Fix oversight in commit 4429f6a9e3e12bb4af6e3677fbc78cd80f160252.

The test name and the following test cases suggest the index created
should be hash index, but it forgot to add 'using hash' in the test case.
This in itself won't improve code coverage as there were some other tests
which were covering the corresponding code.  However, it is better if the
added tests serve their actual purpose.

Reported-by: Paul A Jungwirth
Author: Paul A Jungwirth
Reviewed-by: Mahendra Singh
Backpatch-through: 9.4
Discussion: https://postgr.es/m/CA+renyV=Us-5XfMC25bNp-uWSj39XgHHmGE9Rh2cQKMegSj52g@mail.gmail.com

Branch
------
REL_12_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/fb341a7db9ba03f365bd02dc47123fbad6cc3761

Modified Files
--------------
src/test/regress/expected/rangetypes.out | 2 +-
src/test/regress/sql/rangetypes.sql      | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)