acct.pl: Change name of package in Error message - Bug#12772

- Change package name from squid accounting to proxy accounting in mail Subject line

Fixes: Bug#12772
Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>

src/squid-accounting/acct.pl

@@ -289,7 +289,7 @@ sub sendbill {
 		my $msg = MIME::Lite->new(
 			From	=> $mail{'SENDER'},
 			To		=> $mail{'RECIPIENT'},
-			Subject	=> "ERROR Squid Accounting",
+			Subject	=> "ERROR Proxy Accounting",
 			Type	=> 'multipart/mixed'
 		);