debian/apt.logrotate: keep histories for 12 month

debian/apt.logrotate

@@ -1,5 +1,5 @@
 /var/log/apt/term.log {
-  rotate 6
+  rotate 12
   monthly
   compress
   missingok
@@ -7,7 +7,7 @@
 }
 
 /var/log/apt/history.log {
-  rotate 6
+  rotate 12
   monthly
   compress
   missingok