Revert "added page expires"

This reverts commit f02f3d507dc0959866e6bdef67cc1cf29c0f173e.

system/config/system.yaml

@@ -31,7 +31,6 @@ pages:
       '>': 'gt'
       '<': 'lt'
   types: 'txt|xml|html|json|rss|atom'  # Pipe separated list of valid page types
-  expires: 604800                      # Page expires time in seconds (default 7 days)
 
 cache:
   enabled: true                        # Set to true to enable caching
@@ -42,7 +41,6 @@ cache:
   lifetime: 604800                     # Lifetime of cached data in seconds (0 = infinite)
   gzip: false                          # GZip compress the page output
 
-
 twig:
   cache: true                          # Set to true to enable twig caching
   debug: false                         # Enable Twig debug

system/src/Grav/Common/Grav.php

@@ -298,8 +298,6 @@ class Grav extends Container
         $extension = $this['uri']->extension();
         header('Content-type: ' . $this->mime($extension));
 
-        header('Expires: '.gmdate('D, d M Y H:i:s \G\M\T', time() + $this['config']->get('system.pages.expires')));
-
         // Set debugger data in headers
         if (!($extension === null || $extension == 'html')) {
             $this['debugger']->enabled(false);