DOC - Update 3.11 Backups page to use nodetool refresh instead of import

I've found a typo shown in official Cassandra website when I was looking for Cassandra backup & restore solution. I believe there's no nodetool import option available. It might be nodetool refresh?

https://cassandra.apache.org/doc/3.11/cassandra/operating/backups.html

Restoring from Incremental Backups and Snapshots

The two main tools/commands for restoring a table after it has been dropped are:

• sstableloader
• nodetool import

Ref: https://cassandra.apache.org/doc/3.11/cassandra/tools/nodetool/refresh.html