Fix some grammar in documentation of spgist

Discussion: https://postgr.es/m/92961161-9b49-e42f-0a72-d5d47e0ed4de@postgrespro.ru
Author: Liudmila Mantrova
Reviewed-by: Jonathan Katz, Tom Lane, Michael Paquier
Backpatch-through: 9.4

diff --git a/doc/src/sgml/spgist.sgml b/doc/src/sgml/spgist.sgml
index 56827e520dd62a7a07ac2959e8530143a3fb7dc9..0cd58169aa4c47fab33e071e817751f3a8632434 100644 (file)
--- a/doc/src/sgml/spgist.sgml
+++ b/doc/src/sgml/spgist.sgml
@@ -134,7 +134,7 @@
  
   Of the two operator classes for type point,
   quad_point_ops is the default.  kd_point_ops
-  supports the same operators but uses a different index data structure which
+  supports the same operators but uses a different index data structure that
   may offer better performance in some applications.