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

src/backend/catalog/index.c

@@ -800,11 +800,11 @@ index_create(Relation heapRelation,
 				 errmsg("user-defined indexes on system catalog tables are not supported")));
 
 	/*
-	 * Btree text_pattern_ops uses text_eq as the equality operator, which is
+	 * Btree text_pattern_ops uses texteq as the equality operator, which is
-	 * fine as long as the collation is deterministic; text_eq then reduces to
+	 * fine as long as the collation is deterministic; texteq then reduces to
 	 * bitwise equality and so it is semantically compatible with the other
 	 * operators and functions in that opclass.  But with a nondeterministic
-	 * collation, text_eq could yield results that are incompatible with the
+	 * collation, texteq could yield results that are incompatible with the
 	 * actual behavior of the index (which is determined by the opclass's
 	 * comparison function).  We prevent such problems by refusing creation of
 	 * an index with that opclass and a nondeterministic collation.
@@ -814,7 +814,7 @@ index_create(Relation heapRelation,
 	 * opclasses as incompatible with nondeterminism; but for now, this small
 	 * hack suffices.
 	 *
-	 * Another solution is to use a special operator, not text_eq, as the
+	 * Another solution is to use a special operator, not texteq, as the
 	 * equality opclass member; but that is undesirable because it would
 	 * prevent index usage in many queries that work fine today.
 	 */