Libdoc: Fix workaround for Firefox width bug.
Libdoc: Fix workaround for Firefox width bug.

This affects the usage list in new modal dialogs showing type info.
Without the workaround the list of usages looks something like this:

     First Keyword   , Second Keyword   , Third

The Firefox bug causing this problem is
https://bugzilla.mozilla.org/show_bug.cgi?id=362880

robotframework/robotframework,robotframework/robotframework,robotframework/robotframework,HelioGuilherme66/robotframework,HelioGuilherme66/robotframework,HelioGuilherme66/robotframework