Use a POST with a form body when querying Prometheus. (#2401)

Fixes: https://github.com/lensapp/lens/issues/1352
Signed-off-by: Patrick J McNerthney <pat@mcnerthney.com>

src/main/cluster.ts

@@ -518,7 +518,8 @@ export class Cluster implements ClusterModel, ClusterState {
       timeout: 0,
       resolveWithFullResponse: false,
       json: true,
-      qs: queryParams,
+      method: "POST",
+      form: queryParams,
     });
   }