message: Fix fixed width dialogs
  Move the max-width to the fixedWidth div rather than the dialog,
  otherwise the fixedWidth keeps getting bigger with bigger windows
  but the dialog doesn't so it scrolls.
diff: @@ -268,7 +268,6 @@ textarea {
  font-size: 15px;
  position: relative;
  padding: 25px 30px 30px 30px;
  - max-width: 704px;
  max-height: 80%;
  box-shadow: 2px 15px 30px 0 $dialog-shadow-color;
  border-radius: 4px;
  @@ -277,6 +276,7 @@ textarea {
  .mx_Dialog_fixedWidth {
  width: 60vw;
  + max-width: 704px;
  }
  .mx_Dialog_staticWrapper .mx_Dialog {
  