Remove filegraft from arm.tmpl (#1457906)

It isn't used at all, so remove it instead of crashing.

share/templates.d/99-generic/arm.tmpl

@@ -50,17 +50,9 @@ treeinfo ${basearch} platforms ${platforms}
     %endif
 %endfor
 
-# Inherit iso-graft/ if it exists from external templates
-<%
-    import os
-    if os.path.exists(workdir + "/iso-graft"):
-        filegraft += " " + workdir + "/iso-graft"
-%>
-
 # Add the license files
 %for f in glob("/usr/share/licenses/*-release/*"):
     install ${f} ${f|basename}
-    <% filegraft += " {0}={1}/{0}".format(basename(f), outroot) %>
 %endfor
 
 ## FIXME: ARM may need some extra boot config