update --build-depends help string

[emilypi]

This PR updates the --build-depends help string in repl. Additionally, it looks like my extr-whitespace-stripping macro caught some extraneous whitespace in the file. If you want me to revert, just say so

Please include the following checklist in your PR:

• Patches conform to the coding conventions.
• Any changes that could be relevant to users have been recorded in the changelog (add file to changelog.d directory).
• The documentation has been updated, if necessary.

Please also shortly describe how you tested your change. Bonus points for added tests!

[phadej]

I also pushed a commit to master trimming eol-whitespace, so you could rebase to make diff prettier (and local).

[emilypi]

@phadej done, thanks for your comments