www: remove old cache disable, only used twice and uneeded

(cherry picked from commit 53f6dace)

src/www/diag_backup.php

@@ -32,10 +32,6 @@
 ini_set('max_execution_time', '0');
 ini_set('max_input_time', '0');
 
-/* omit no-cache headers because it confuses IE with file downloads */
-$omit_nocacheheaders = true;
-$nocsrf = true;
-
 require_once("guiconfig.inc");
 require_once("interfaces.inc");
 require_once("filter.inc");

src/www/guiconfig.inc

@@ -86,15 +86,6 @@ function html_safe($text)
     return htmlspecialchars($text, ENT_QUOTES | ENT_HTML401);
 }
 
-/* make sure nothing is cached */
-if (isset($omit_nocacheheaders) && $omit_nocacheheaders) {
-    header("Expires: 0");
-    header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
-    header("Cache-Control: no-store, no-cache, must-revalidate");
-    header("Cache-Control: post-check=0, pre-check=0", false);
-    header("Pragma: no-cache");
-}
-
 header("X-Frame-Options: SAMEORIGIN");
 
 set_language();

src/www/legacy_traffic_stats.php

@@ -27,7 +27,7 @@
     ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     POSSIBILITY OF SUCH DAMAGE.
 */
-$omit_nocacheheaders = true;
+
 require_once('guiconfig.inc');
 require_once('interfaces.inc');
 require_once('pfsense-utils.inc');