Remove pipeline editor button from blob view

What does this MR do and why?

Now that we have the split button enabled by default, we can remove the side pipeline editor button to avoid having 2 options that lead to the same page.

The reason why we don't need to update any test is because this button was a temporary solution, so we knew we would remove it. The Web IDE split button already has the right tests.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Go to the repository view
2. Go on a root CI config
3. Notice that there are no longer any "pipeline editor" button
4. Notice that in the dropdown of the split button, there is now an option for pipeline editor

MR acceptance checklist

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