pgsql: Fix small inconsistencies in catalog definition of multirange op

Fix small inconsistencies in catalog definition of multirange operators

This commit fixes the description of a couple of multirange operators and
oprjoin for another multirange operator.  The change of oprjoin is more
cosmetic since both old and new functions return the same constant.

These cosmetic changes don't worth catalog incompatibility between 14beta2
and 14beta3.  So, catversion isn't bumped.

Discussion: https://postgr.es/m/CAPpHfdv9OZEuZDqOQoUKpXhq%3Dmc-qa4gKCPmcgG5Vvesu7%3Ds1w%40mail.gmail.com
Backpatch-throgh: 14

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/768ea9bcf98120eef01a6deea9c5c6997b153ab1

Modified Files
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src/include/catalog/pg_operator.dat | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)