On `AlertsDashboard`, recent work to support LineString selection seems to have messed up Polygon event listeners

[rudokemper]

Current Buggy or Suspicious Behavior

Currently, there is an issue where hovering over an alert polygon does not change the mouse to a pointer any longer. This is likely due to code introduced by https://github.com/ConservationMetrics/guardianconnector-views/pull/37 to support LineString interactivity on the dashboard, specifically the new handleBufferMouseEvent method which is currently set to only work with LineString layers.

Steps to Reproduce

• Hover the mouse over a polygon.
• Notice that the mouse doesn't change to a pointer.
• The click event does trigger the sidebar state change, however.

Expected Behavior

• Mouse should change to pointer when hovering over a polygon.