Fix duplicate master entries in the mr versions dropdown
What does this MR do?
Fixes bug when "master" was duplicated per each mr version in the dropdown
Are there points in the code the reviewer needs to double check?
no
Screenshots (if relevant)
Before
After
What are the relevant issue numbers?
Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/22519, Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/22715