branch_protection_rules nudge is hostile to browsing back

[jsoref]

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Bug

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in #23046, people complained about the general ux of the branch protection nudge.

I decided to follow the nudge to add a rule, and then after, I used 🔙 which took me to:
https://github.com/check-spelling/spell-check-this/settings/branch_protection_rules

I expect to be able to go back and not get a 404

If necessary, the page could (temporarily) redirect me to:
https://github.com/check-spelling/spell-check-this/settings/branches

which is where I could then manage my branch protection rules.

Ideally, branch_protection_rules should exist and should let me compare my rules for various branches, but that's outside the scope of this request.