Make new test immune to collation

Animals running in Czech locale failed.  I could try to find table names
that don't have this problem, but it seems simpler to just use the C
locale.

Per buildfarm

src/test/regress/expected/triggers.out

@@ -3425,7 +3425,7 @@ alter trigger a on grandparent rename to b;
 select tgrelid::regclass, tgname,
 (select tgname from pg_trigger tr where tr.oid = pg_trigger.tgparentid) parent_tgname
 from pg_trigger where tgrelid in (select relid from pg_partition_tree('grandparent'))
-order by tgname, tgrelid::regclass::text;
+order by tgname, tgrelid::regclass::text COLLATE "C";
    tgrelid   | tgname | parent_tgname 
 -------------+--------+---------------
  chi         | b      | b
@@ -3452,7 +3452,7 @@ alter trigger p on grandparent rename to q;
 select tgrelid::regclass, tgname,
 (select tgname from pg_trigger tr where tr.oid = pg_trigger.tgparentid) parent_tgname
 from pg_trigger where tgrelid in (select relid from pg_partition_tree('grandparent'))
-order by tgname, tgrelid::regclass::text;
+order by tgname, tgrelid::regclass::text COLLATE "C";
    tgrelid   | tgname | parent_tgname 
 -------------+--------+---------------
  chi         | b      | b

src/test/regress/sql/triggers.sql

@@ -2589,7 +2589,7 @@ alter trigger a on grandparent rename to b;
 select tgrelid::regclass, tgname,
 (select tgname from pg_trigger tr where tr.oid = pg_trigger.tgparentid) parent_tgname
 from pg_trigger where tgrelid in (select relid from pg_partition_tree('grandparent'))
-order by tgname, tgrelid::regclass::text;
+order by tgname, tgrelid::regclass::text COLLATE "C";
 alter trigger a on only grandparent rename to b;	-- ONLY not supported
 alter trigger b on middle rename to c;	-- can't rename trigger on partition
 create trigger c after insert on middle
@@ -2603,7 +2603,7 @@ alter trigger p on grandparent rename to q;
 select tgrelid::regclass, tgname,
 (select tgname from pg_trigger tr where tr.oid = pg_trigger.tgparentid) parent_tgname
 from pg_trigger where tgrelid in (select relid from pg_partition_tree('grandparent'))
-order by tgname, tgrelid::regclass::text;
+order by tgname, tgrelid::regclass::text COLLATE "C";
 
 drop table grandparent;