fix test collection

Author: vincentsarago

tests/data/test_collection.json

@@ -92,7 +92,7 @@
     "temporal": {
       "interval": [
         [
-          "2013-06-01",
+          "2013-06-01T00:00:00Z",
           null
         ]
       ]
@@ -149,4 +149,4 @@
       "url": "https://element84.com"
     }
   ]
-}
+}