Fix unrelated failing test

Author: DePasqualeOrg

packages/client/test/client/auth-extensions.test.ts

@@ -305,7 +305,7 @@ describe('createPrivateKeyJwtAuth', () => {
 
         const params = new URLSearchParams();
         await expect(addClientAuth(new Headers(), params, 'https://auth.example.com/token', undefined)).rejects.toThrow(
-            /Invalid character/
+            /cannot be part of a valid base64/
         );
     });