PLT-2036 - Enabling popover on mobile (#3742)

webapp/sass/responsive/_mobile.scss

@@ -290,8 +290,9 @@
         }
     }
 
-    .search-help-popover.visible {
-        visibility: hidden;
+    .search-help-popover {
+        left: 55px;
+        max-width: calc(100% - 10px);
     }
 
     .modal-direct-channels {

webapp/sass/responsive/_tablet.scss

@@ -26,6 +26,7 @@
 
             .search-bar__container {
                 padding-right: 8px;
+                z-index: 5;
             }
         }
     }