MAINTAINERS: Drop outdated FPGA Manager website

The rocketboards website no longer really reflects a good landing
place for people interested in FPGA Manager.

Cc: Xu Yilun <yilun.xu@intel.com>
Cc: Wu Hao <hao.wu@intel.com>
Acked-by: Xu Yilun <yilun.xu@intel.com>
Signed-off-by: Moritz Fischer <mdf@kernel.org>

MAINTAINERS

@@ -7342,7 +7342,6 @@ M:	Xu Yilun <yilun.xu@intel.com>
 R:	Tom Rix <trix@redhat.com>
 L:	linux-fpga@vger.kernel.org
 S:	Maintained
-W:	http://www.rocketboards.org
 Q:	http://patchwork.kernel.org/project/linux-fpga/list/
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/mdf/linux-fpga.git
 F:	Documentation/devicetree/bindings/fpga/