Remove unused variable from template_preprocess_page()

Problem/Motivation

+++ b/core/includes/theme.inc
@@ -1779,15 +1781,6 @@ function template_preprocess_page(&$variables) {
-  // Set up layout variable.
-  $variables['layout'] = 'none';
-  if (!empty($variables['page']['sidebar_first'])) {
-    $variables['layout'] = 'first';
-  }
-  if (!empty($variables['page']['sidebar_second'])) {
-    $variables['layout'] = ($variables['layout'] == 'first') ? 'both' : 'second';
-  }
-

$variables['layout'] appears to be unused and undocumented.

Proposed resolution

Remove it

Remaining tasks

-Write a patch
-Make sure it doesn't break anything / testing

User interface changes

-

API changes

-