Externalize i18n strings from blob/show.html.haml

What does this MR do and why?

Externalizes i18n strings from app/views/projects/blob/show.html.haml

Credit goes to @chu4zu9 for starting this in !49119 (closed)

Screenshots or screen recordings

N/A

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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