i2ptunnel: Remove dup headers in error pages

apps/i2ptunnel/resources/proxy/ahelper-conflict-header.ht

 HTTP/1.1 409 Conflict
 Content-Type: text/html; charset=UTF-8
-Referrer-Policy: no-referrer
 Cache-Control: no-cache
 Connection: close
 X-XSS-Protection: 1; mode=block

apps/i2ptunnel/resources/proxy/ahelper-new-header.ht

 HTTP/1.1 409 New Address
 Content-Type: text/html; charset=UTF-8
-Referrer-Policy: no-referrer
 Cache-Control: no-cache
 Connection: close
 X-XSS-Protection: 1; mode=block

apps/i2ptunnel/resources/proxy/dnfh-header.ht

 HTTP/1.1 500 Domain Not Found
 Content-Type: text/html; charset=UTF-8
-Referrer-Policy: no-referrer
 Cache-Control: no-cache
 Connection: close
 X-XSS-Protection: 1; mode=block
@@ -34,4 +33,4 @@ _("Seeing this page often? See {0}the FAQ{1} for help in {2}adding some subscrip
 </p>
 <hr>
 <span><b>_("Could not find the following destination:")</b>
-</span>
+</span>