Remove some dead code

src/utils/abortHandle.ts

@@ -1,18 +0,0 @@
-/*
-Copyright 2025 New Vector Ltd.
-
-SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
-Please see LICENSE in the repository root for full details.
-*/
-
-export class AbortHandle {
-  public constructor(private aborted = false) {}
-
-  public abort(): void {
-    this.aborted = true;
-  }
-
-  public isAborted(): boolean {
-    return this.aborted;
-  }
-}