fix: skip redundant batch.apply (#17816)

tiny fix — just realised we're calling `this.apply()` (via
`this.activate()`) unnecessarily, since it will happen again immediately
after in `flush_effects`

.changeset/vast-dolls-dance.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: skip redundant batch.apply

packages/svelte/src/internal/client/reactivity/batch.js

@@ -340,7 +340,7 @@ export class Batch {
 
 	flush() {
 		if (queued_root_effects.length > 0) {
-			this.activate();
+			current_batch = this;
 			flush_effects();
 		} else if (this.#pending === 0 && !this.is_fork) {
 			// append/remove branches