Fix Project variable query

Author: mhuguesaws

batch-grafana-cost-dashboard.json

@@ -468,7 +468,7 @@
             "region": "__default"
           },
           "format": 1,
-          "rawSQL": "select $__column from $__table;",
+          "rawSQL": "SELECT DISTINCT $__column FROM $__table WHERE COALESCE($__column, '') <> '';",
           "table": "awsbatchcostreport"
         },
         "refresh": 1,
@@ -508,4 +508,4 @@
   "uid": "5e7i8l_4k",
   "version": 41,
   "weekStart": ""
-}
+}