Horizontal Scrollbar Appears on Theme Info Page in Mobile Viewports

[yogeshbhutkar]

Issue Description:
A horizontal scrollbar appears on the Theme Installation page when viewed on mobile viewports. This causes the content to shift left when scrolled horizontally, despite the content being correctly contained within the viewport. The horizontal scroll functionality is unnecessary and disrupts the user experience.

Root Cause:
The issue arises from a right margin applied to theme screenshots to ensure proper grid alignment on desktop views. However, this margin is not adjusted for mobile viewports, resulting in the unintended horizontal scrollbar.

Steps to Reproduce:

1. Navigate to the Themes section.
2. Select any theme from the list and observe the horizontal scrollbar on mobile viewports.

Proposed Solution:
Remove the right margin for smaller viewports. Adjusting the CSS to handle margins based on the viewport size dynamically will resolve the issue and eliminate the horizontal scrollbar.

[yogeshbhutkar]

Screencast of the bug.

### Description:
This PR fixes an unexpected horizontal scroll detected on mobile viewports under the Theme Info page.

Trac ticket: https://core.trac.wordpress.org/ticket/62607

### Screenshot of the changes:

[parthvataliya]

Test Report

Description

This report validates whether the indicated patch works as expected.

Patch tested: ​https://patch-diff.githubusercontent.com/raw/WordPress/wordpress-develop/pull/7918.patch

Environment

• WordPress: 6.8-alpha-59274-src
• PHP: 8.2.26
• Server: nginx/1.27.3
• Database: mysqli (Server: 8.0.40 / Client: mysqlnd 8.2.26)
• Browser: Chrome 131.0.0.0
• OS: Linux
• Theme: Twenty Twenty-Five 1.0
• MU Plugins: None activated
• Plugins:
  • Test Reports 1.2.0

Actual Results

1. ✅ Issue resolved with patch.

[yogeshbhutkar]

Duplicate of #62411.