Fix linking to new issue with selected template

What does this MR do?

Fix linking to new issue with selected template with issuable_template URL parameter.

Are there points in the code the reviewer needs to double check?

• http://localhost:3000/gitlab-org/gitlab-ce/issues/new?issuable_template=Bug

Why was this MR needed?

Using the issuable_template URL parameter has no effect.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #26595 (closed)