[go_router] Fix Incorrect URL after pop twice

[leehack]

The URL doesn't match to the route when it pops twice or more due to the pattern mismatch.

When it pops from /one/two/three, it goes to /one/two/ instead of /one/two.
From the next pops, it can't match the pattern due to the / at the end of the path.
With the fix, it just makes sure to match two/ as well.

flutter/flutter#117431

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[chunhtai]

Thanks for submitting this pr, but we already have a fix waiting for review #2952

[leehack]

@chunhtai, I'm still wondering if we could merge this as a hotfix since it's pretty small so that we can address the issue quickly while the PR is being reviewed unless it will be merged shortly. I saw the PR is removing the function I modified, so the conflict will also be minimal. What do you think?

[chunhtai]

I think it should be merged shortly