system test: fix home directory reference

Author: neolynx

system/t06_publish/PublishSnapshot43Test_gold

@@ -5,7 +5,7 @@ Signing file 'Release' with gpg, please enter your passphrase when prompted:
 Clearsigning file 'Release' with gpg, please enter your passphrase when prompted:
 
 Snapshot snap43 has been successfully published.
-Please setup your webserver to serve directory '/home/runner/.aptly/public' with autoindexing.
+Please setup your webserver to serve directory '${HOME}/.aptly/public' with autoindexing.
 Now you can add following line to apt sources:
   deb http://your-server/ maverick main
 Don't forget to add your GPG key to apt with apt-key.