BLEnder fix(@types/node): drop bogus BinaryLike cast in emailHashPrefix

emailHashPrefix cast its already-string argument to crypto's BinaryLike
before passing it to getSha1, which takes a string. In @types/node 26 that
union (string | NodeJS.ArrayBufferView) is no longer accepted where a string
is required, breaking tsc for npm-lint, npm-build and the Docker image build.
Removed the unnecessary cast and the now-unused BinaryLike import. No
behaviour change.

Author: mozilla-blender[bot]

src/app/api/utils/mockUtils.ts

@@ -2,12 +2,11 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-import { BinaryLike } from "crypto";
 import { getSha1 } from "../../../utils/fxa";
 import { logger } from "../../functions/server/logging";
 
 export function emailHashPrefix(email: string) {
-  return getSha1(email as BinaryLike)
+  return getSha1(email)
     .slice(0, 6)
     .toUpperCase();
 }