libstdc++: testsuite: fix dg-bogus directive syntax

These dg-bogus directives were bogus as they missed a closing brace.

```
+PASS: 23_containers/array/capacity/empty.cc  -std=gnu++17  (test for bogus messages, line 54)
 PASS: 23_containers/array/capacity/empty.cc  -std=gnu++17 (test for excess errors)
 PASS: 23_containers/array/capacity/empty.cc  -std=gnu++17 execution test
+PASS: 23_containers/array/capacity/max_size.cc  -std=gnu++17  (test for bogus messages, line 54)
 PASS: 23_containers/array/capacity/max_size.cc  -std=gnu++17 (test for excess errors)
 PASS: 23_containers/array/capacity/max_size.cc  -std=gnu++17 execution test
+PASS: 23_containers/array/capacity/size.cc  -std=gnu++17  (test for bogus messages, line 54)
```

libstdc++-v3/ChangeLog:
	PR libstdc++/101831

	* testsuite/23_containers/array/capacity/empty.cc: Add missing brace.
	* testsuite/23_containers/array/capacity/max_size.cc: Ditto.
	* testsuite/23_containers/array/capacity/size.cc: Ditto.