GitLab UI: 872-merge-glskeletonloading-into-glskeletonloader integration test

What does this MR do?

Updates a snapshot test to account for changes to GLSkeletonLoader. The markup for this snapshot test shouldn't actually be changing but originally it was taken using shallowMount which caused the snapshot to use the component stub. With VTU component stubs display props as HTML attributes. Since we added some props to the GLSkeletonLoader component it causes the test to fail. This MR changes to using mount as it seems like a more reliable test in this case.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
  • Developer facing change, no changelog needed
• [-] 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