Fix whitespace changes visibility when the related file was initially collapsed

What does this MR do?

This MR fixes a bug on MR diff page. Currently when file is too long and is initially collapsed and hiding of whitespace changes is enabled, this setting has no effect and whitespace changes are still shown. This MR fixes it by adding a parameter to URL used to fetching collapsed diff.

This is actually my first MR and quiet rushed (sorry :( ), because i wanted to submit it before the deadline of Hackathon.

@rpaik Can you help me to find a reviewer?

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance 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

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 #50106 (closed)