Fix missing slash in common-api of entity. The mistype was introduced in rP14588.
It wasn't found because it's not used at all. It was added in rP12343, and its usage was removed in rP13687.
Patch By: Angen
Differential Revision: https://code.wildfiregames.com/D1994
Also there are occurrences in rP14865 and rP15153.