Be more permissive in brin regression tests.

Upstream postgres will probably soon push some changes that will change the
semantics of explain_get_index_name_hook_type.  The returned index name will
automatically be properly quoted if needed, while it was previously the
extension's duty to take care of that, which hypopg failed to do.  See
discussion at https://postgr.es/m/flat/16502-57bd1c9f913ed1d1%40postgresql.org
for more details.

To avoid build failure when the change is committed, change brin regression
test to match an hypothetical index name whether is quoted or not, similarly to
how it's done in all other regression tests.

expected/hypo_brin.out

@@ -12,7 +12,7 @@ FROM public.hypopg_create_index('CREATE INDEX ON hypo_brin USING brin (id);');
 -- Should use hypothetical index
 SET enable_seqscan = 0;
 SELECT COUNT(*) FROM do_explain('SELECT * FROM hypo_brin WHERE id = 1') e
-WHERE e ~ 'Bitmap Index Scan on <\d+>brin_hypo_brin.*';
+WHERE e ~ 'Bitmap Index Scan.*<\d+>brin_hypo_brin.*';
  count 
 -------
      1

test/sql/hypo_brin.sql

@@ -13,6 +13,6 @@ FROM public.hypopg_create_index('CREATE INDEX ON hypo_brin USING brin (id);');
 -- Should use hypothetical index
 SET enable_seqscan = 0;
 SELECT COUNT(*) FROM do_explain('SELECT * FROM hypo_brin WHERE id = 1') e
-WHERE e ~ 'Bitmap Index Scan on <\d+>brin_hypo_brin.*';
+WHERE e ~ 'Bitmap Index Scan.*<\d+>brin_hypo_brin.*';
 
 DROP TABLE hypo_brin;