Remove usage of webcrypto from node:crypto in Node 18

The original code was intended to shim in support for the webcrypto
interface in Node 18, which was included indirectly as `webcrypto`
in the "node:crypto" module or globally via the
`--no-experimental-global-webcrypto` flag.

This change has caused many issues with bundlers and static analyzers
which do not like the obfuscated call to `require()`.

Node 18 will no longer receive security support as of 30 April 2025[1]
and as such it feels like we can now drop this workaround in favor of
documenting alternative approaches.

[1]: https://endoflife.date/nodejs

Author: aron

lib/util.js

@@ -97,24 +97,6 @@ async function validateWebhook(requestData, secret) {
  */
 async function createHMACSHA256(secret, data) {
   const encoder = new TextEncoder();
-  let crypto = globalThis.crypto;
-
-  // In Node 18 the `crypto` global is behind a --no-experimental-global-webcrypto flag
-  if (typeof crypto === "undefined" && typeof require === "function") {
-    // NOTE: Webpack (primarily as it's used by Next.js) and perhaps some
-    // other bundlers do not currently support the `node` protocol and will
-    // error if it's found in the source. Other platforms like CloudFlare
-    // will only support requires when using the node protocol.
-    //
-    // As this line is purely to support Node 18.x we make an indirect request
-    // to the require function which fools Webpack...
-    //
-    // We may be able to remove this in future as it looks like Webpack is getting
-    // support for requiring using the `node:` protocol.
-    // See: https://github.com/webpack/webpack/issues/18277
-    crypto = require.call(null, "node:crypto").webcrypto;
-  }
-
   const key = await crypto.subtle.importKey(
     "raw",
     base64ToBytes(secret),