Always set checked_monotonic_time when calling CheckMonotonicTime()

src/timer/unix/SDL_systimer.c

@@ -73,7 +73,7 @@ static void CheckMonotonicTime(void)
     struct timespec value;
     if (clock_gettime(SDL_MONOTONIC_CLOCK, &value) == 0) {
         has_monotonic_time = true;
-    } else
+    }
 #elif defined(SDL_PLATFORM_APPLE)
     if (mach_timebase_info(&mach_base_info) == 0) {
         has_monotonic_time = true;