test: fix syntax error in test-dns-idna2008.js when failing

Fixes a bug I introduced in 9613221
PR-URL: #26570
Refs: #25870
Refs: #26473
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

Author: refack

test/internet/test-dns-idna2008.js

@@ -32,13 +32,15 @@ dns.lookup(fixture.hostname, mustCall((err, address) => {
 assert.strictEqual(address,fixture.expectedAddress);
 }));
 
-dns.promises.lookup(fixture.hostname).then(mustCall(({ address })=>{
+dns.promises.lookup(fixture.hostname).then(({ address })=>{
 assert.strictEqual(address,fixture.expectedAddress);
-}).catch((err)=>{
+},(err)=>{
 if(err&&err.errno==='ESERVFAIL'){
 assert.ok(err.message.includes('queryA ESERVFAIL straße.de'));
+}else{
+throwerr;
 }
-}));
+}).finally(mustCall());
 
 dns.resolve4(fixture.hostname,mustCall((err,addresses)=>{
 assert.ifError(err);