Ignore failures in fontmgr_iter angle/gpu GM tests on Windows

expectations/gm/Test-Win7-ShuttleA-HD2000-x86-Release-DirectWrite/expected-results.json

 {
   "actual-results": {
     "failed": null, 
     "failure-ignored": null, 
     "no-comparison": null, 
     "succeeded": null
   }, 
   "expected-results": {
     "3x3bitmaprect_565.png": {
       "allowed-digests": [
@@ skipping 5837 matching lines @@
       "reviewed-by-human": false
     }, 
     "fontmgr_iter_gpu.png": {
       "allowed-digests": [
         [
           "bitmap-64bitMD5", 
           3589296463987175181
         ]
       ], 
       "bugs": [
-        1578
+        1597
       ], 
+      "ignore-failure": true, 
       "reviewed-by-human": false
     }, 
     "fontmgr_match_565.png": {
       "allowed-digests": [
         [
           "bitmap-64bitMD5", 
           6912355345607947791
         ]
       ], 
       "bugs": [
@@ skipping 4923 matching lines @@
           13996013494185391731
         ]
       ], 
       "bugs": [
         1578
       ], 
       "reviewed-by-human": false
     }
   }
 }