Fix comment in test

The comment was apparently copy-and-pasted and did not reflect the
actual test outcome.

src/test/regress/expected/alter_generic.out

@@ -505,7 +505,7 @@ CREATE STATISTICS alt_stat1 ON a, b FROM alt_regress_1;
 CREATE STATISTICS alt_stat2 ON a, b FROM alt_regress_1;
 ALTER STATISTICS alt_stat1 RENAME TO alt_stat2;   -- failed (name conflict)
 ERROR:  statistics object "alt_stat2" already exists in schema "alt_nsp1"
-ALTER STATISTICS alt_stat1 RENAME TO alt_stat3;   -- failed (name conflict)
+ALTER STATISTICS alt_stat1 RENAME TO alt_stat3;   -- OK
 ALTER STATISTICS alt_stat2 OWNER TO regress_alter_generic_user2;  -- failed (no role membership)
 ERROR:  must be member of role "regress_alter_generic_user2"
 ALTER STATISTICS alt_stat2 OWNER TO regress_alter_generic_user3;  -- OK

src/test/regress/sql/alter_generic.sql

@@ -442,7 +442,7 @@ CREATE STATISTICS alt_stat1 ON a, b FROM alt_regress_1;
 CREATE STATISTICS alt_stat2 ON a, b FROM alt_regress_1;
 
 ALTER STATISTICS alt_stat1 RENAME TO alt_stat2;   -- failed (name conflict)
-ALTER STATISTICS alt_stat1 RENAME TO alt_stat3;   -- failed (name conflict)
+ALTER STATISTICS alt_stat1 RENAME TO alt_stat3;   -- OK
 ALTER STATISTICS alt_stat2 OWNER TO regress_alter_generic_user2;  -- failed (no role membership)
 ALTER STATISTICS alt_stat2 OWNER TO regress_alter_generic_user3;  -- OK
 ALTER STATISTICS alt_stat2 SET SCHEMA alt_nsp2;    -- OK