openocd: drop system_groups

Now that we have plugdev as a system group, we don't need to create it here.

srcpkgs/openocd/template

@@ -1,7 +1,7 @@
 # Template file for 'openocd'
 pkgname=openocd
 version=0.11.0
-revision=3
+revision=4
 build_style=gnu-configure
 configure_args="
  --disable-werror
@@ -49,8 +49,6 @@ homepage="http://openocd.org/"
 distfiles="${SOURCEFORGE_SITE}/${pkgname}/${pkgname}-${version}.tar.bz2"
 checksum=43a3ce734aff1d3706ad87793a9f3a5371cb0e357f0ffd0a151656b06b3d1e7d
 
-system_groups="plugdev"
-
 CFLAGS="-fcommon"
 
 post_install() {