[FIX] web: statusbar: border color for disabled buttons

Before this commit, the intent was to change the border color
of the first button that appears when the status bar is disabled.

The problem was that this added a border for all buttons and
not only the (visually) first one.

addons/web/static/src/scss/form_view.scss

@@ -222,6 +222,9 @@
                 &:last-child {
                     padding-left: $o-horizontal-padding - 1;
                     border-left: 1px solid gray('400');
+                    &.disabled {
+                        border-color: gray('300');
+                    }
                 }
 
                 &:active {
@@ -232,7 +235,6 @@
                     opacity: 1.0;
                     color: $text-muted;
                     pointer-events: none;
-                    border-left: 1px solid gray('300');
                 }
 
                 &:not(:first-child):before, &:not(:first-child):after {