XAFORUM-97 : The "All forums" livetable is not well displayed on FF32 on...

... 6.2
* We shouldn't increase the selector's specificity by providing both a generic selector and a class selector. The class selector is sufficient. 
* The problem should be specific to the Forum Application, not the Livetable one. If it was a problem with the Livetable should be fixed in Livetable's component, not here.
* Careful on the indentation. We are using 2 spaces to indent, not a tab formed of 4 spaces.

* This is not the solution to the problem :) Please review the Pull Request