Delete fixed size for error screen in order to adapt for smaller resolutions

Bug: 1002108
Change-Id: Id4473becaafe6e6d2477dfae0aad1aa2b4fd1669
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1850512Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Commit-Queue: Thomas Tellier <tellier@google.com>
Cr-Commit-Position: refs/heads/master@{#704584}

chrome/browser/resources/chromeos/login/screen_error_message.css

@@ -2,10 +2,6 @@
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file. */
 
-#error-message {
-  width: 768px;
-}
-
 .show-with-ui-state-update,
 .show-with-ui-state-signin,
 .show-with-ui-state-supervised,