Refactor the _skip-trial view specs

What does this MR do?

As part of !40564 (merged) I had at one point added some code to the ee/app/views/trials/_skip_trial.html.haml view partial and updated its specs with those changes as well as doing a bit of a refactor on those specs. Later on, the changes to the view were removed but I thought it worthwhile to keep the overall spec refactor work.

No changelog or documentation is necessary as these changes are entirely developer-facing.

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

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Loosely related to #215852 (closed)