User with read_code: true are shown WebIDE button

What I see

A user viewing a private repository who has the Guest role + read_code permission sees the "WebIDE" button to edit the file in WebIDE.

What I would expect to see instead

Since these are guest users with read only permissions, the button can likely be hidden for them.

Steps to reproduce

Create a guest user who can read_code using instructions in !104322 (diffs)

Or, ask Jessie Young to add you as a Guest+1 on a test project

For Guest+1, WebIDE button will be displayed but return a 404 if the user tries to open the file