gui: Fix tooltips on buttons inside button groups (ref #7984) (#9008)

As per Bootstrap recommendation, buttons with tooltips inside button
groups require to have container: 'body' set. This prevents tooltips
from causing the buttons to jump on hover and also allows the tooltips
to be wider instead of wrapping on every space.

Ref: https://getbootstrap.com/docs/3.3/components/#btn-groups

Signed-off-by: Tomasz Wilczyński <twilczynski@naver.com>

gui/default/assets/css/overrides.css

@@ -574,13 +574,6 @@ html[lang|="ko"] i {
     font-style: normal;
 }
 
-/* Prevent buttons from jumping up and down
-   when a tooltip is shown for one of them. */
-.btn-group-vertical > .tooltip + .btn,
-.btn-group-vertical > .tooltip + .btn-group {
-    margin-top: -1px;
-}
-
 .select-on-click {
     -webkit-user-select: all;
     user-select: all;