Use native caching system

src/_port

@@ -70,12 +70,6 @@ _port() {
     '*:extra:->extra' \
     && return 0
 
-  local cache_policy
-  zstyle -s ":completion:${curcontext}:" cache-policy cache_policy
-  if [[ -z "$cache_policy" ]]; then
-    zstyle ":completion:${curcontext}:" cache-policy _port_caching_policy
-  fi
-
   case "$state" in
     extra)
       case "$words[2]" in
@@ -139,11 +133,4 @@ _port_select() {
   fi
 }
 
-_port_caching_policy() {
-  local reg_time comp_time
-  reg_time=$(stat -c '%Z' $port_prefix/var/macports/registry/registry.db)
-  comp_time=$(stat -c '%Z' $1)
-  return $(( reg_time < comp_time ))
-}
-
 _port "$@"