Clean up headers

Updates headers to match style guide and makes them consistent
throughout pages in the GUI. Removes instances where a header
element existed and a different header style was being applied.
For example, <h2 class="h4">

Tested: Ran GUI locally and verified that headers look consistent
and have the appropriate sizing while using Chrome, Firefox and
Safari.

Change-Id: I187136298ed2bfd36c40c2b80d5a4f20947cbe56
Signed-off-by: beccabroek <beccabroek@gmail.com>
diff --git a/app/common/directives/errors.html b/app/common/directives/errors.html
index f3e98b6..49ed449 100644
--- a/app/common/directives/errors.html
+++ b/app/common/directives/errors.html
@@ -4,7 +4,7 @@
         <div class="screen-reader-offscreen modal-description">{{dataService.errorModalDetails.title}}</div><!-- accessibility only; used for screen readers -->
         <div class="page-header ">
             <span class="icon icon__warning inline"><span class="accessible-text" role="alert">{{dataService.errorModalDetails.title}}</span></span>
-            <h1 class="modal-title h4 inline">{{dataService.errorModalDetails.title}}</h1>
+            <h3 class="modal-title inline">{{dataService.errorModalDetails.title}}</h3>
         </div>
         <div class="modal__content">
             <p>{{dataService.errorModalDetails.description}}</p>