fix linter issues in benchmark tests

pkg/weightedrand/weightedrand_test.go

@@ -47,7 +47,7 @@ func BenchmarkMultiple(b *testing.B) {
 					b.ResetTimer()
 
 					for i := 0; i < b.N; i++ {
-						chs.PickRandom()
+						_, _ = chs.PickRandom()
 					}
 				})
 			})
@@ -86,7 +86,7 @@ func BenchmarkSingle(b *testing.B) {
 				for i := 0; i < b.N; i++ {
 					// never actually do this, this is not how the library is used
 					chs, _ := NewChooser(wr_menshen_choices...)
-					chs.PickRandom()
+					_, _ = chs.PickRandom()
 				}
 			})
 		})