Remove hatch installation in js/app/package.json which is no longer needed

[whitphx]

Description

Delete a snippet which was added in #7855 to make the test pass in a non-main branch. It's no longer needed as the PR was merged.

[gradio-pr-bot]

🪼 branch checks and previews

•	Name	Status	URL
	Spaces	ready!	Spaces preview
	Website	building...
	Storybook	ready!	Storybook preview
:unicorn:	Changes	detected!	Details

---

Install Gradio from this PR

pip install https://gradio-builds.s3.amazonaws.com/93c4fbfbc6e6704fbcfc55aa54d8716e977a296b/gradio-4.28.3-py3-none-any.whl

Install Gradio Python Client from this PR

pip install "gradio-client @ git+https://github.com/gradio-app/gradio@93c4fbfbc6e6704fbcfc55aa54d8716e977a296b#subdirectory=client/python"

[gradio-pr-bot]

🦄 change detected

This Pull Request includes changes to the following packages.

Package	Version
@gradio/app	patch
gradio	patch

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

With the following changelog entry.

Remove hatch installation in js/app/package.json which is no longer needed

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/gradio-app/gradio/edit/fix/revert-hatch-installation/.changeset/calm-goats-sit.md).

[whitphx]

UI test fails with a weird diff 👀

[pngwn]

This is just flake. It takes a second for the preview panel to render. You can approve it and move on. We need to figure out some of the flake in the visual tests.