Add padding in SupervisedUserErrorPage.

This cl adds padding in supervised user error page.

Bug: 1045152
Change-Id: Ic0e06df7b53dabf178b67b592526b2ec3cc84307
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2023196Reviewed-by: Aga Wronska <agawronska@chromium.org>
Commit-Queue: Yilkal Abe <yilkal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735644}

chrome/browser/supervised_user/supervised_user_error_page/resources/supervised_user_block_interstitial.css

@@ -10,6 +10,7 @@ body {
   --header-color:  #202124;
   --paragraph-color: #5f6368;
   font-family: "Roboto", sans-serif;
+  padding: 24px 24px 20px 24px;
 }
 
 button {