esm: mark importAssertions as required

We already always specify a value, and failing to do so would likely be
a bug.

PR-URL: #46164
Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

lib/internal/modules/esm/loader.js

@@ -299,15 +299,11 @@ class ESMLoader {
    * @param {string} originalSpecifier The specified URL path of the module to
    *                                   be resolved.
    * @param {string} [parentURL] The URL path of the module's parent.
-   * @param {ImportAssertions} [importAssertions] Assertions from the import
+   * @param {ImportAssertions} importAssertions Assertions from the import
    *                                              statement or expression.
    * @returns {Promise<{ format: string, url: URL['href'] }>}
    */
-  async resolve(
-    originalSpecifier,
-    parentURL,
-    importAssertions = { __proto__: null },
-  ) {
+  async resolve(originalSpecifier, parentURL, importAssertions) {
     if (this.#hooks) {
       return this.#hooks.resolve(originalSpecifier, parentURL, importAssertions);
     }