[alter_table-test] Increase assertion timeout

On ubuntu 22.04 release build, AlterReplicationFactorWhileWriting test
failed with timeout. So timeout was increased to 60 seconds.

Change-Id: Ifc51365a798569c22e680eb3e7723a5f330d43c5
Reviewed-on: http://gerrit.cloudera.org:8080/21347
Tested-by: Kudu Jenkins
Reviewed-by: Attila Bukor <abukor@apache.org>
1 file changed