Pull requests approval

Hi there! I wonder if it is possible to do a simple approve of PR. I have a fork and would like to merge a branch from the fork into the master. When I have several reviewers it is impossible to mark this PR as approved - only merge/rebase choices. So could you give me some tips how to do simple approve without merge?

Click top tab files changed and you can find a green button on top right, then you can approve the PR.