Updated commands in Delete Key Value Pair and Combiner that were outdated

[Amemeda]

Combiner:

• "$ bin/accumulo shell -u username" updated to "$ accumulo shell -u root"
• added "username@instance examples.runners> config -t examples.runners -s table.class.loader.context=file:///path/to/accumulo-examples/target/accumulo-examples.jar" before setiter command

Delete Key Value Pair

• "$ /path/to/accumulo shell -u username -p secret" up updated to "$ accumulo shell --user root --password secret" in 3 locations
• "$ /path/to/accumulo rfile-info -d hdfs://localhost/accumulo/tables/1t/default_tablet/F00007em.rf" updated to "$ accumulo file rfile-info -d hdfs://localhost/accumulo/tables/1t/default_tablet/F00007em.rf" in 3 locations

[DomGarguilo]

Looks like this got closed automatically when I deleted the branch it was targeting. The main branch now targets Accumulo 4.x so you'll need to reopen this PR and change the target branch to that.