fix(apps.public.cloud.theme): increase navbar z-index (#1165)

ref: MBP-541

Author: ganeshkumar1989

packages/manager/apps/public-cloud/src/assets/theme/_navbar.less

@@ -8,7 +8,7 @@
 .oui-navbar {
   background-color: #fff;
   box-shadow: 0 2pt 4pt rgba(17, 63, 109, 0.15);
-  z-index: 2;
+  z-index: 3;
 
   .oui-navbar__brand {
     color: rgb(40, 89, 192);