LG-8402: Add a cancel link to the in-person proofing barcode page

[sheldon-b]

🎫 Ticket

LG-8402

🛠 Summary of changes

• Adds a cancel link to the in-person proofing barcode page. This link redirects the user to the existing start over page.
• Note: the designs call for a 32px gap between the horizontal but that doesn't match other cancel links in the application. I've kept the consistency with the other pages.

👀 Screenshots

If relevant, include a screenshot or screen capture of the changes.

Before:

After:

[svalexander]

LGTM

[allthesignals]

Just added an idea for re-using a partial somewehre else but looks good to me.....

[allthesignals]

Noticed that there's a shared partial for this (app/views/idv/doc_auth/_cancel.html.erb) and wonder if it could be re-used instead, or re-using this (app/views/shared/_cancel.html.erb) instead...

[sheldon-b]

Yeah, the reason I didn't use those is that they use a different text string for the link text ("Cancel" instead of "Cancel your barcode"). I considered adding a link text parameter to one of those but it didn't seem worth it since we're only doing this in one place and it doesn't seem likely that we'll want to do it elsewhere with different text again