test: fix seedless-onboarding mock encryptor

Author: mikesposito

packages/seedless-onboarding-controller/tests/mocks/vaultEncryptor.ts

@@ -86,7 +86,7 @@ export default class MockVaultEncryptor
 
   async keyFromPassword(
     password: string,
-    salt: string = this.DEFAULT_SALT,
+    salt: string,
     exportable: boolean = true,
     opts: KeyDerivationOptions = this.DEFAULT_DERIVATION_PARAMS,
   ) {
@@ -218,4 +218,8 @@ export default class MockVaultEncryptor
     const result = await this.decryptWithKey(key, payload);
     return result;
   }
+
+  generateSalt(): string {
+    return this.DEFAULT_SALT;
+  }
 }