fix: layout main part left padding.

[riccox]

Types of changes

• New feature
• Bug fix
• Documentation change
• Coding style change
• Refactoring
• Performance improvement
• Test cases
• Continuous integration
• Typescript definition change
• Breaking change

Background and context

Using arco-cli to create a pro project, and start it without any changes.
There is obvious wrong left padding at main content part.

Solution

Found wrong left padding setting in layout code.
Just unset them.

How is the change tested?

Changelog

Changelog(CN)	Changelog(EN)	Related issues

Checklist:

• Provide changelog for relevant changes (e.g. bug fixes and new features) if applicable.
• Changes are submitted to the appropriate branch (e.g. features should be submitted to feature branch and others should be submitted to main branch)

Other information