docs: remove loading dialog section from quickstart guide

[sy-records]

Summary

After merging #1466, I discovered #1458 (comment).

It seems that data-app does not currently have any practical use? And there is a new Loading.

Perhaps data-app is used in Vue. However, I tested it without adding it, and it worked fine.

So I removed this part of the content.

Related issue, if any:

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

For any code change,

• Related documentation has been updated, if needed
• Related tests have been added or updated, if needed

Does this PR introduce a breaking change?

• Yes
• No

Tested in the following browsers:

• Chrome
• Firefox
• Safari
• Edge

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Name	Status	Preview	Comments	Updated (UTC)
docsify-preview	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Aug 7, 2025 2:34am

[Koooooo-7]

In the v4, the Loading dialog support customize the Loading content even inserting DOMs.

<div id="app"> I'm loading ... </div>

For now when we change the content, we'll see the loading effect and the content mess up.
I suppose we should have a fix on it...

[sy-records]

Modifying it requires adding some styles.

docsify/src/themes/shared/_app.css

Lines 126 to 133 in 77d93fa

	#app {
	display: flex;
	align-items: center;
	justify-content: center;
	gap: 0.75em;
	height: 100vh;
	padding-inline: 50px;
	}

There is a new loading screen in v5. I think we can remove it without fixing it.

[Koooooo-7]

There is a new loading screen in v5. I think we can remove it without fixing it.

Cuz I thought it was a feature in v4 that user can customize the loading page easily.
I'm ok with it to remove this feature, if user urges to add it back, we could refine it then.