Removes leading space from hover state in graph links

#### What are the relevant issue numbers?
Closes #21123 

#### Screenshots (if relevant)
![Screen_Shot_2016-08-24_at_8.35.15_AM](/uploads/2dc583391f87c6d0a67f0535967c637f/Screen_Shot_2016-08-24_at_8.35.15_AM.png)

See merge request !5980