Revert "allow dynamically loading available mailboxes"

This reverts commit 2cb2fa0345.

bin/mw

@@ -226,7 +226,7 @@ getboxes() { if [ -n "${force+x}" ] ; then
 		idnum=$((idnum + 1))
 		[ "$idnum" -eq "$x" ] || break
 	done
-	toappend="mailboxes \`mdir=$maildir/$fulladdr/; find \$mdir -mindepth 1 -type d -name cur | sed -e 's:/cur\$:\":' -e \"s:\$mdir:\\\"=:\" | sort | tr '\\\n' ' '\`"
+	toappend="mailboxes $(echo "$mailboxes" | sed "s/^/\"=/;s/$/\"/" | paste -sd ' ' - )"
 }
 
 finalize() { echo "$toappend" >> "$accdir/$fulladdr.muttrc"