chore: don't transfer #blocking_pending and discard callbacks in #merge

Neither is needed for any test, unlike the #pending transfer — worth a closer look.

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

@@ -621,21 +621,11 @@ export class Batch {
 		}
 
 		this.#pending += batch.#pending;
-		if (batch.#blocking_pending !== null) {
-			const blocking_pending = (this.#blocking_pending ??= new Map());
-			for (const [effect, count] of batch.#blocking_pending) {
-				blocking_pending.set(effect, (blocking_pending.get(effect) ?? 0) + count);
-			}
-		}
 
 		for (const c of batch.#commit_callbacks) {
 			this.oncommit(() => c(batch));
 		}
 
-		for (const c of batch.#discard_callbacks) {
-			this.ondiscard(() => c(batch));
-		}
-
 		for (const [s, v] of batch.#skipped_branches) {
 			this.#skipped_branches.set(s, v);
 			this.unskipped_branches.delete(s);