Fix error styling in smart card SAML PIN dialog

Fix the error font and position according to the latest UX feedback:
* increase the font size to 12;
* remove the bold weight from the font;
* move the error label up, so that the distance from the input field to
  it is only 4px.

Bug: 1024251
Test: use DevTools to check the font, take a screenshot to check the margins
Change-Id: I631f2fab46270251d0e980480c21b4d37fb479e1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2002874Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Commit-Queue: Maksim Ivanov <emaxx@chromium.org>
Cr-Commit-Position: refs/heads/master@{#732947}

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

@@ -18,11 +18,10 @@
 
 #errorContainer {
   color: var(--google-red-600);
-  font-size: 10px;
-  font-weight: 500;
+  font-size: 12px;
   position: absolute;
   text-align: center;
-  top: 40px;
+  top: 36px;
   width: 100%;
 }