Remove selection after copy of code
- Follows https://gitlab.com/gitlab-com/gitlab-docs/merge_requests/235
- Clear text selection when copied to clipboard
Slack thread: https://gitlab.slack.com/archives/C16HYA2P5/p1522695464000144?thread_ts=1522678327.000272&cid=C16HYA2P5
Edited by Marcia Ramos