[libcxx][test] explicitly discard bitset::test's return

... just in case some implementation annotates it `[[nodiscard]]`.

GitOrigin-RevId: 9f8ca86a87a73c4fba6f8f229008117f7d0f35ab
diff --git a/test/std/utilities/template.bitset/bitset.members/test.out_of_range.pass.cpp b/test/std/utilities/template.bitset/bitset.members/test.out_of_range.pass.cpp
index 1289015..7c05d2a 100644
--- a/test/std/utilities/template.bitset/bitset.members/test.out_of_range.pass.cpp
+++ b/test/std/utilities/template.bitset/bitset.members/test.out_of_range.pass.cpp
@@ -19,15 +19,18 @@
 int main(int, char**) {
     {
         std::bitset<0> v;
-        try { v.test(0); assert(false); } catch (std::out_of_range const&) { }
+        try { (void) v.test(0); assert(false); }
+        catch (std::out_of_range const&) { }
     }
     {
         std::bitset<1> v("0");
-        try { v.test(2); assert(false); } catch (std::out_of_range const&) { }
+        try { (void) v.test(2); assert(false); }
+        catch (std::out_of_range const&) { }
     }
     {
         std::bitset<10> v("0000000000");
-        try { v.test(10); assert(false); } catch (std::out_of_range const&) { }
+        try { (void) v.test(10); assert(false); }
+        catch (std::out_of_range const&) { }
     }
 
     return 0;