Resolve "Account expiration date/time discrepancy"

What does this MR do?

The date above the subscription table is a UTC date, whereas the Trial end date in the subscription table is displayed in local time. Depending on the user's timezone, there might be a difference between these two dates which might lead to confusion.

This MR creates a UTC date for Trial end date in order to avoid any UI discrepancies.

Thanks @rdavila for debugging and coming up with a fix in https://gitlab.com/gitlab-org/gitlab-ee/issues/8946#note_130014787

Screenshots:

before	after

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ee/issues/8946

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• EE specific content should be in the top level /ee folder
• For a paid feature, have we considered GitLab.com plans, how it works for groups, and is there a design for promoting it to users who aren't on the correct plan?
• Security reports checked/validated by reviewer

Closes #8946 (closed)