fix small bug when join src & api_prefix

[Chandler-Bing]

Update client.py

Description

fix a samll bug, previous version will ignore root path. will cause error in some specifial way

before

import urllib
src = 'https://demo.com/root_path/'
api_prefix = '/gradio'
src_prefixed = urllib.parse.urljoin(src, api_prefix).rstrip("/") + "/"
print(src_prefixed)
# https://demo.com/gradio/

actually we want it to be
https://demo.com/root_path/gradio/

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[gradio-pr-bot]

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---

Install Gradio from this PR

pip install https://gradio-pypi-previews.s3.amazonaws.com/248dc748610fa4b4d84a5dee3a276b7cdacabedd/gradio-5.6.0-py3-none-any.whl

Install Gradio Python Client from this PR

pip install "gradio-client @ git+https://github.com/gradio-app/gradio@248dc748610fa4b4d84a5dee3a276b7cdacabedd#subdirectory=client/python"

Install Gradio JS Client from this PR

npm install https://gradio-npm-previews.s3.amazonaws.com/248dc748610fa4b4d84a5dee3a276b7cdacabedd/gradio-client-1.8.0.tgz

Use Lite from this PR

<script type="module" src="https://gradio-lite-previews.s3.amazonaws.com/248dc748610fa4b4d84a5dee3a276b7cdacabedd/dist/lite.js""></script>

[gradio-pr-bot]

🦄 change detected

This Pull Request includes changes to the following packages.

Package	Version
gradio	minor
gradio_client	minor

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fix small bug when join src & api_prefix

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