MT#64132 wrapper.sh: no longer invoke grml-live with arch specific option

The command line option -a to set the architecture to build is no longer
supported as of
9a903deb8d

The running architecture is used by default, so drop the -a option in
preparation for the upcoming grml-live releases.

Change-Id: I60c205c20c5df1515ddac3d7d3c532307e7c2234

wrapper.sh

@@ -93,7 +93,6 @@ build_command+=" LIVE_CONF=/code/grml-live/etc/grml/grml-live.conf"
 build_command+=" GRML_FAI_CONFIG=${fai_config}"
 build_command+=" ./grml-live"
 build_command+=" -s '${osversion}'"
-build_command+=" -a amd64"
 build_command+=" -i '${iso_image_name}'"
 build_command+=" -c SIPWISE,PUPPETLABS"
 build_command+=" -o /grml/"