Fix encoding error

[xu-song]

Description

with gr.Blocks(css="css/style.css", js="js/onload.js") as demo:
    pass

  File "C:\Users\xusong\Miniconda3\envs\py3.10\lib\site-packages\gradio\blocks.py", line 791, in __init__
    self.js = js_file.read()
UnicodeDecodeError: 'gbk' codec can't decode byte 0xa4 in position 543: illegal multibyte sequence

Closes: #8076, #7856

Tests

1. PRs will only be merged if tests pass on CI. To run the tests locally, please set up your Gradio environment locally and run the tests: bash scripts/run_all_tests.sh

2. You may need to run the linters: bash scripts/format_backend.sh and bash scripts/format_frontend.sh

[gradio-pr-bot]

🪼 branch checks and previews

•	Name	Status	URL
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:unicorn:	Changes	detecting...

---

Install Gradio from this PR

pip install https://gradio-builds.s3.amazonaws.com/ac97ef9f07194218795c767f9a065d01f5abe85f/gradio-4.31.5-py3-none-any.whl

Install Gradio Python Client from this PR

pip install "gradio-client @ git+https://github.com/gradio-app/gradio@ac97ef9f07194218795c767f9a065d01f5abe85f#subdirectory=client/python"

Install Gradio JS Client from this PR

npm install https://gradio-builds.s3.amazonaws.com/ac97ef9f07194218795c767f9a065d01f5abe85f/gradio-client-0.19.4.tgz

[gradio-pr-bot]

🦄 change detected

This Pull Request includes changes to the following packages.

Package	Version
gradio	patch

• [ ] Maintainers can select this checkbox to manually select packages to update.

With the following changelog entry.

Fix encoding error

Maintainers or the PR author can modify the PR title to modify this entry.

#### Something isn't right?

- Maintainers can change the version label to modify the version bump. - If the bot has failed to detect any changes, or if this pull request needs to update multiple packages to different versions or requires a more comprehensive changelog entry, maintainers can [update the changelog file directly](https://github.com/xu-song/gradio/edit/patch-2/.changeset/common-zoos-retire.md).