Remove fedora image from dib status

We are no longer building these images so don't need them on the dib
status grafana dashboard any longer. This dashboard lists all images in
graphite to generate a list of images to produce statuses for. We
exclude the fedora images using a negative lookahead regex.

Change-Id: I2d7ba7984c98ec103142fa23e3a7b31e9d1c7485

grafana/nodepool-dib-status.json

@@ -475,7 +475,7 @@
         "options": [],
         "query": "stats.timers.nodepool.dib_image_build.*",
         "refresh": 1,
-        "regex": "",
+        "regex": "/^(?!fedora-[0-9]+).*/",
         "skipUrlSync": false,
         "sort": 0,
         "type": "query"
@@ -492,4 +492,4 @@
   "uid": "f3089338b3",
   "version": 9,
   "weekStart": ""
-}
+}