Allow multiple images for flaky dashing GM on intel/win7/gpu

expectations/gm/base-shuttle-win7-intel-directwrite/expected-results.json

 {
   "actual-results": {
     "failed": null, 
     "failure-ignored": null, 
     "no-comparison": null, 
     "succeeded": null
   }, 
   "expected-results": {
     "aaclip_gpu.png": {
       "allowed-digests": [
@@ skipping 1801 matching lines @@
           "bitmap-64bitMD5", 
           15857302678163965353
         ]
       ], 
       "ignore-failure": false
     }, 
     "dashing_gpu.png": {
       "allowed-digests": [
         [
           "bitmap-64bitMD5", 
+          11137490508568328458
+        ],
+        [
+          "bitmap-64bitMD5", 
           4904536750140494702
         ]
       ], 
       "ignore-failure": false
     }, 
     "degeneratesegments_565.png": {
       "allowed-digests": [
         [
           "bitmap-64bitMD5", 
           5037191661353682037
@@ skipping 2107 matching lines @@
     "xfermodes_gpu.png": {
       "allowed-digests": [
         [
           "bitmap-64bitMD5", 
           13632669295194296329
         ]
       ], 
       "ignore-failure": false
     }
   }
-}
+}