Fix collation dependency in test introduced in 8586bf7ed8.

Per buildfarm.

src/test/regress/expected/create_am.out

@@ -173,7 +173,7 @@ SELECT
         (SELECT 'toast for ' || relname::regclass FROM pg_class pcm WHERE pcm.reltoastrelid = pc.oid)
     ELSE
         relname::regclass::text
-    END AS relname
+    END COLLATE "C" AS relname
 FROM pg_class AS pc,
     pg_am AS pa
 WHERE pa.oid = pc.relam
@@ -183,8 +183,8 @@ ORDER BY 3, 1, 2;
 ---------+--------+----------------------------------
  r       | heap2  | tableam_parted_b_heap2
  r       | heap2  | tableam_parted_d_heap2
- r       | heap2  | tableam_tblas_heap2
  r       | heap2  | tableam_tbl_heap2
+ r       | heap2  | tableam_tblas_heap2
  m       | heap2  | tableam_tblmv_heap2
  t       | heap2  | toast for tableam_parted_b_heap2
  t       | heap2  | toast for tableam_parted_d_heap2

src/test/regress/sql/create_am.sql

@@ -123,7 +123,7 @@ SELECT
         (SELECT 'toast for ' || relname::regclass FROM pg_class pcm WHERE pcm.reltoastrelid = pc.oid)
     ELSE
         relname::regclass::text
-    END AS relname
+    END COLLATE "C" AS relname
 FROM pg_class AS pc,
     pg_am AS pa
 WHERE pa.oid = pc.relam