k_scoped_scheduler_lock_and_sleep: Mark class as [[nodiscard]]

Prevents logic bugs from slipping through.

src/core/hle/kernel/k_scoped_scheduler_lock_and_sleep.h

@@ -15,7 +15,7 @@
 
 namespace Kernel {
 
-class KScopedSchedulerLockAndSleep {
+class [[nodiscard]] KScopedSchedulerLockAndSleep {
 public:
     explicit KScopedSchedulerLockAndSleep(KernelCore& kernel, KThread* t, s64 timeout)
         : kernel(kernel), thread(t), timeout_tick(timeout) {