Merge branch 'remove-errors-scss' into 'master'

Remove unused errors css

`.error-page` isn't being used anywhere as far as I can see so I removed it

See merge request !7933

app/assets/stylesheets/pages/errors.scss

-.error-page {
-  max-width: 400px;
-  margin: 0 auto;
-
-  h1,
-  h2,
-  h3 {
-    text-align: center;
-  }
-
-  h1 {
-    font-size: 56px;
-    line-height: 100px;
-    font-weight: 300;
-  }
-}