[wip/mk/sysdep/libgraphviz] Correct packages names

Correct Fedora and Debian names to match with real names.
Error reported by Robert Bulk, corrected thanks to Anthony

mk/sysdep/libgraphviz.mk

@@ -36,8 +36,8 @@ SYSTEM_SEARCH.libgraphviz=	\
 	'lib/pkgconfig/libgvc.pc'\
 	'lib/libgvc.so:/Version/s/[^.0-9]//gp'
 
-SYSTEM_PKG.Fedora.libgraphviz=	libgraphviz-devel
-SYSTEM_PKG.Ubuntu.libgraphviz=	graphviz-dev
+SYSTEM_PKG.Fedora.libgraphviz=	graphviz-devel
+SYSTEM_PKG.Ubuntu.libgraphviz=	libgraphviz-dev
 SYSTEM_PKG.Debian.libgraphviz=	graphviz-dev
 SYSTEM_PKG.NetBSD.libgraphviz=	pkgsrc/graphics/graphviz