Bug 1909441 - webauthn on macOS: use user.displayName rather than user.name, as intended r=jschanck

This was probably just a copy/paste issue. The intent was to use the
displayName for the displayName parameter when creating a cross-platform
webauthn credential on macOS.

Differential Revision: https://phabricator.services.mozilla.com/D218466

dom/webauthn/MacOSWebAuthnService.mm

@@ -585,7 +585,7 @@ MacOSWebAuthnService::MakeCredential(uint64_t aTransactionId,
         NSString* userNameNS = nsCocoaUtils::ToNSString(userName);
 
         nsAutoString userDisplayName;
-        Unused << aArgs->GetUserName(userDisplayName);
+        Unused << aArgs->GetUserDisplayName(userDisplayName);
         NSString* userDisplayNameNS = nsCocoaUtils::ToNSString(userDisplayName);
 
         nsTArray<int32_t> coseAlgs;