Make 'Cancel' in CI/CD editor redirect to project

What does this MR do?

This makes the Cancel button in the new CI/CD editor redirect to the project home instead of resetting the form. The reason is that while a reset is nice, the Cancel button should cancel the editing like on other create/edit pages (merge requests, issues, releases, ...) rather than resetting the form.

Related to #331916 (closed)

Steps to test

1. Go to a project
2. Go to the CI/CD editor (/-/ci/editor)
   • Sidebar: CI/CD -> Editor
3. optional if there is no .gitlab-ci.yml on the default branch: click on Create new CI/CD pipeline
4. Enter some characters in the code area
5. Click on the Cancel button at the bottom of the page
6. See that you are redirected to the project

• before: editor is reset to the last state (empty if there is no CI config)

Screenshots (strongly suggested)

Affected component (no visual changes, button red-outlined)

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• [-] I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• [-] I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.