chore: slightly better comment

Author: paoloricciuti

packages/svelte/src/internal/client/runtime.js

@@ -689,7 +689,7 @@ export function flushSync(fn) {
 
 		if (queued_root_effects.length === 0) {
 			// this would be reset in `flush_queued_root_effects` but since we are early returning here,
-			// we need to reset it here as well
+			// we need to reset it here as well in case the first time there's 0 queued root effects
 			is_flushing = false;
 			last_scheduled_effect = null;
 			if (DEV) {