Fixed hidden truncated diff lines not showing when expanded
Fixed hidden truncated diff lines not showing when expanded

`truncated_diff_lines` gets added to collapsed discussions when expanded
at this point `truncated_diff_lines` doesn't exist and is therefore not
reactive. This property gets added when creating discussions in order
for it to start as a reactive property

dreampet/gitlab,axilleas/gitlabhq,axilleas/gitlabhq,stoplightio/gitlabhq,axilleas/gitlabhq,mmkassem/gitlabhq,dreampet/gitlab,axilleas/gitlabhq,iiet/iiet-git,dreampet/gitlab,iiet/iiet-git,iiet/iiet-git,stoplightio/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,mmkassem/gitlabhq,iiet/iiet-git,mmkassem/gitlabhq,stoplightio/gitlabhq,dreampet/gitlab