Resolve "MR right sidebar is off when scrollbars are visible"

What does this MR do?

Takes over the community contribution but replaces it with the solution that completely removes the secondary scrollbar in the right sidebar.

Screenshots

Option — "Show scroll bars" setting set to "Always" in MacOS settings.

	Before with Option ON	After with Option OFF	After with Option ON
Issue
MR
Board

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Closes #196226 (closed)