ci,tests: silence compilation warning for vlib/v/tests/testcase_leak.vv

Author: spytheman

vlib/v/tests/testcase_leak.vv

@@ -8,5 +8,6 @@ fn main() {
 	mut y := unsafe { malloc(1000) }
 	// unsafe { free(y) } // leak if commented out
 	y = unsafe { nil }
+	_ = y
 	gc_check_leaks()
 }