RJournal.layout: package 'url' is already provided

This fixes an option conflict error when using
RJournal.sty v0.12 (the newest).

Previous versions of the .sty also provided 'url'
so they should still work with the layout.
Update RJournal.layout to v0.12 of RJournal.sty

Without this, the template gives a BibTeX error because
there are two \bibstyle commands in the .aux.

This would have broken backwards compatibility but RJournal.layout
has not yet been in a LyX release. Further, the journal made a
significant change (moving to a single column instead of two)
so any submitter would need to update the .sty anyway.