Hide table lines in macOS dark mode

Hide lines because SWT table and trees flash white when dragging columns
and/or expanding/collapsing nodes.

Issue: eclipse-platform/eclipse.platform.swt#273

name.abuchen.portfolio.ui/css/dark_mac.css

@@ -6,3 +6,14 @@
 @import url("platform:/plugin/name.abuchen.portfolio.ui/css/shared/mac.css");
 
 @import url("platform:/meta/name.abuchen.portfolio.ui/custom.css");
+
+/*
+Hide lines in macOS dark mode because SWT table and trees flash white
+when dragging columns and/or expanding/collapsing nodes.
+
+See https://github.com/eclipse-platform/eclipse.platform.swt/issues/273
+*/
+Table,
+Tree {
+	swt-lines-visible: false;
+}