Various style fixes (#13534)

* Various style fixes

- Fix the rest of the monochrome borders for arc-green
- Fix close icon position on system notice modal and padding
- Fix selectable table color for arc-green

* proper fix for close icon

Co-authored-by: Lauris BH <lauris@nix.lv>

web_src/less/_admin.less

@@ -1,5 +1,7 @@
 .admin {
-  padding-top: 15px;
+  &.notice {
+    padding-top: 15px;
+  }
 
   .table.segment {
     padding: 0;