acct.en.pl: Update to use proxy accounting - Bug#12772

-Replace the variable names used for the accounting page with proxy accounting in a
  consistent manner
- Tested on a vm system and confirmed to have a consistent naming approach now

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

src/squid-accounting/acct.en.pl

@@ -110,7 +110,7 @@
 'acct name' => 'Description',
 'acct no data' => 'No Data available',
 'acct rrdsize' => 'Size of Bill directory',
-'acct settings' => 'Accounting settings',
+'acct settings' => 'Proxy Accounting settings',
 'acct skipurl' => 'Skip these URLs (Intranet)',
 'acct status' => 'Status',
 'acct str' => 'Street',
@@ -122,7 +122,7 @@
 'acct tel' => 'Telephone',
 'acct tls' => 'Use TLS',
 'acct traffic monthly' => 'Monthly data volume',
-'acct title' => 'Webproxy Accounting',
+'acct title' => 'Proxy Accounting',
 'acct usemail' => 'Send bills via Mail',
 'acct usermulti' => 'is already in group',
 'acct ustid' => 'USt-ID',