tagme: Do not use git push --tags

Summary:
It's dangerous, as it will push all local tags. Getting rid off unwanted
tags on the remote is not the best type of work to start your day...

Use git push origin <tag_name> instead, which will only push the
desired tag.

As has happened in kdevelop.git

Reviewers: O2 releaseme, sitter, bcooksley

Reviewed By: O2 releaseme, sitter

Differential Revision: https://phabricator.kde.org/D19578