Approve from pull request should be removed when someone pushes new changes

Example:

My collegoue add me a code to check, I approved the pull request. Later someone pushed other commits to that pull request that wasn't checked by anyone but the pull request still keeps its Approved flag. In this state if i look to the pull request it looks like it is checked and approved to me, but it may contains some critical errors pushed after the approval.

Solution:
When someone pushes changes to open PR, the approved flag from all users should be removed.