Fix root url resolution from x_forwarded_host headers

[abidlabs]

Oversight on my part -- if we are using x_forwarded_host header to construct the root url, we should not be stripping the trailing characters belonging to the route_url.

I've added a test and the fix has been confirmed by users in #7724 and #7774

Closes: #7774
Closes: #7724

[gradio-pr-bot]

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Install Gradio from this PR

pip install https://gradio-builds.s3.amazonaws.com/2f1c470d3bc2357a1def1297a267669ef2f4f981/gradio-4.22.0-py3-none-any.whl

Install Gradio Python Client from this PR

pip install "gradio-client @ git+https://github.com/gradio-app/gradio@2f1c470d3bc2357a1def1297a267669ef2f4f981#subdirectory=client/python"

[gradio-pr-bot]

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Fix root url resolution from x_forwarded_host headers

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[abidlabs]

Thanks @freddyaboulton for reviewing!

[rwb-truelime]

Thanks for fixing! 🚀