@W-23478197 - fix: set upload command to hidden by default

[william-xie-sf]

What does this PR do?

Sets visibility of the new upload command to hidden by default.

william.xie@... plugin-ui-bundle-dev % sf ui-bundle --help
 ›   Warning: @salesforce/plugin-ui-bundle-dev is a linked ESM module and cannot be auto-transpiled. Existing compiled
 ›    source will be used instead.
Work with UI bundles

USAGE
  $ sf ui-bundle COMMAND

COMMANDS
  ui-bundle dev  Preview a UI bundle locally and in real-time, without deploying it to your org.

What issues does this PR fix or reference?

@W-23478197@