setup.ssh: keep the newline when commenting out AcceptEnv

The $ in /(^\s*AcceptEnv.*$)/ matches before the newline, so $1 did not
contain it and the following line was appended to the comment - which
commented out the Subsystem sftp line on a stock Debian sshd_config.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

setup.ssh

@@ -9,7 +9,7 @@ while(<IN>) {
   if (/^\s*\#*\s*PermitRootLogin/) {
     $out.="PermitRootLogin yes\n" ;
   } elsif (/(^\s*AcceptEnv.*$)/) {
-    $out.="#$1";
+    $out.="#$1\n";
   } else {
     $out.=$_;
   }