update: remove root command, cleanup tests

General MR

Summary

In prep for future work (auto updating bbctl and beyond), clean up the old, unused root command for bbctl update.

Relevant logs/screenshots

danieldides@BPH-MAC14 ~/P/b/p/bbctl (dd/cleanup-bbctl-update)> bbctl update
msg: No update functionality has been implemented yet

Linked Issue

closes #296 (closed)

Upgrade Notices

N/A

added statusreview label

assigned to @daniel.dides

requested review from @nicole.dupree, @ryan.daily, @leedarrien, @daniel.dides, @ryan.lesher, @chris.oconnell, @rehank125, @andrewshoell, @dpritchettrm, @mgoloski, and @jfoster

removed review request for @daniel.dides

approved this merge request

mentioned in commit 2b21bc22

merged