fix(certificatemanager): Increase wait time for DNS validation

Allow the Lambda function to wait up to 9 minutes and 20 seconds before
bailing out waiting for the domain to be validated. It used to be
waiting no more than 5 minutes and would occasionally timeout on users.

Fixes #2914 (hopefully)

packages/@aws-cdk/aws-certificatemanager/lambda-packages/dns_validated_certificate_handler/lib/index.js

@@ -140,10 +140,10 @@ const requestCertificate = async function (requestId, domainName, subjectAlterna
 
   console.log('Waiting for validation...');
   await acm.waitFor('certificateValidated', {
-    // Wait up to 5 minutes
+    // Wait up to 9 minutes and 30 seconds
     $waiter: {
       delay: 30,
-      maxAttempts: 10
+      maxAttempts: 19
     },
     CertificateArn: reqCertResponse.CertificateArn
   }).promise();