replace broken links to mysqlhighavailability.com (#1039)

Author: serprex

replication/event.go

@@ -427,12 +427,12 @@ type GTIDEvent struct {
 SequenceNumber int64
 
 // ImmediateCommitTimestamp/OriginalCommitTimestamp are introduced in MySQL-8.0.1, see:
-// https://mysqlhighavailability.com/replication-features-in-mysql-8-0-1/
+// https://dev.mysql.com/blog-archive/new-monitoring-replication-features-and-more
 ImmediateCommitTimestamp uint64
 OriginalCommitTimestamp uint64
 
 // Total transaction length (including this GTIDEvent), introduced in MySQL-8.0.2, see:
-// https://mysqlhighavailability.com/taking-advantage-of-new-transaction-length-metadata/
+// https://dev.mysql.com/blog-archive/taking-advantage-of-new-transaction-length-metadata
 TransactionLength uint64
 
 // ImmediateServerVersion/OriginalServerVersion are introduced in MySQL-8.0.14, see