Create index on srt table in citext regression tests.

Comments and the tests make clear that the intent is to test with
and without an index, but there was no index.

contrib/citext/expected/citext.out

@@ -325,6 +325,7 @@ VALUES ('aardvark'),
        ('aba'),
        ('ABC'),
        ('abd');
+CREATE INDEX srt_name ON srt (name);
 -- Check the min() and max() aggregates, with and without index.
 set enable_seqscan = off;
 SELECT MIN(name) AS "AAA" FROM srt;

contrib/citext/expected/citext_1.out

@@ -325,6 +325,7 @@ VALUES ('aardvark'),
        ('aba'),
        ('ABC'),
        ('abd');
+CREATE INDEX srt_name ON srt (name);
 -- Check the min() and max() aggregates, with and without index.
 set enable_seqscan = off;
 SELECT MIN(name) AS "AAA" FROM srt;

contrib/citext/sql/citext.sql

@@ -127,6 +127,8 @@ VALUES ('aardvark'),
        ('ABC'),
        ('abd');
 
+CREATE INDEX srt_name ON srt (name);
+
 -- Check the min() and max() aggregates, with and without index.
 set enable_seqscan = off;
 SELECT MIN(name) AS "AAA" FROM srt;