add removing functionality in voting mechanism

[sabrimete]

The PR for the issue: https://github.com/bounswe/bounswe2022group7/issues/548

This is the initial information about comment(same logic applies for discussion post):

This is the result after sending the same vote to remove (it works like youtube like/dislike):

[askabderon]

LGTM, thanks for working on this @sabrimete