Fix cut-off dropdown in board breadcrumbs

What does this MR do and why?

Remove class that caused 'isolate' css property to be added to

Screenshots or screen recordings

before	after

How to set up and validate locally

• Load board in subgroup
• Click ... on breadcrumbs

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

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