Remove unused variable

Co-authored-by: Nina Satragno <nsatragno@gmail.com>
diff --git a/webauthn/helpers.js b/webauthn/helpers.js
index f714b0b3..27a5613 100644
--- a/webauthn/helpers.js
+++ b/webauthn/helpers.js
@@ -514,7 +514,6 @@
     // rawId
     assert_idl_attribute(cred, "rawId", "should return PublicKeyCredential with rawId attribute");
     assert_readonly(cred, "rawId", "should return PublicKeyCredential with readonly rawId attribute");
-    rawId = cred.rawId;
     assert_equals(cred.id, base64urlEncode(new Uint8Array(cred.rawId)), "should return PublicKeyCredential with id attribute set to base64 encoding of rawId attribute");
 
     // type