Adjust sed command for clarity.

debian/changelog

@@ -12,6 +12,9 @@ livecd-rootfs (2.577) UNRELEASED; urgency=medium
       when invoked.
     - Install lxd snap in unminimize.
 
+  [ Steve Langasek ]
+  * Adjust sed command for clarity.
+
  -- Tobias Koch <tobias.koch@canonical.com>  Thu, 11 Apr 2019 17:25:25 +0200
 
 livecd-rootfs (2.576) disco; urgency=medium

live-build/functions

@@ -448,7 +448,7 @@ _snap_post_process() {
                 # Remove snap, assertions and entry in seed.yaml
                 rm -f ${snaps_dir}/snapd_[0-9]*.snap
                 rm -f ${assertions_dir}/snapd_[0-9]*.assert
-                sed --in-place -E 'N;/name: snapd/,+2d' $seed_yaml
+                sed -i -e'/name: snapd/,+2d' $seed_yaml
             fi
             ;;
         *)