Do not show confidential notes checkbox for users with access level less than REPORTER

What does this MR do and why?

We are going to allow only reporter+ users to create confidential notes, this MR hides the checkbox to mark a note as confidential to users without access.

We should also not allow confidential notes being created by guests. This is going to be handled by !98588 (merged).

Before

After

related to #363045 (comment 1110036970)

How to validate locally

1. Create project/group
2. Add a user as guest
3. Go to an epic or issue comment box
4. Confidential checkbox from the screenshot above should not be visible
5. Promote the same user to reporter
6. Confidential checkbox should now be visible

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.