Move SettingsDialog width override to fixedWidth

Move the width overrides to the container so it's the same thing
dictating its size as the rest of the dialogs

res/css/views/dialogs/_SettingsDialog.scss

@@ -16,8 +16,6 @@ limitations under the License.
 
 .mx_SettingsDialog {
     .mx_Dialog {
-        max-width: 1000px;
-        width: 90%;
         height: 80%;
         border-radius: 4px;
         padding-top: 0;
@@ -46,5 +44,10 @@ limitations under the License.
         .mx_Dialog_fixedWidth {
             width: 100%;
         }
+
+        .mx_Dialog_fixedWidth {
+            max-width: 1000px;
+            width: 90%;
+        }
     }
 }