Default to target=_blank for report comment links

[marcaaron]

cc @Jag96

Quick fix here. Couldn't think of any reason why we'd need to open a report comment link in app for now so providing defaults for now to prevent people from getting stuck viewing files in the desktop app. Discussed with @Jag96 and the only reason we could think of is that file downloads will bypass the default "Save as..." prompt that shows in Electron. But there's no clear reason why it's better to do that than just opening these links in Chrome for now.

This logic might need to change if we have report comments that are intended to deep link to various places in the app. But that seems like a future problem.

Fixed Issues

Fixes https://github.com/Expensify/Expensify/issues/142225

Tests

1. Send yourself a .zip attachment and a .txt attachment
2. Attempt to open both in web and desktop platforms
3. Verify they always open in a new external browser window

Screenshots

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