Remove suppressions in ignored-tests.txt

expectations/gm/Test-Win8-ShuttleA-GTX660-x86-Release/expected-results.json

 {
   "expected-results": {
     "3x3bitmaprect_565.png": {
       "allowed-digests": [
         [
           "bitmap-64bitMD5", 
           12831071530564277917
         ]
       ], 
       "bugs": [
@@ skipping 6460 matching lines @@
           "bitmap-64bitMD5", 
           1459541977125271085
         ]
       ], 
       "reviewed-by-human": true
     }, 
     "convex_poly_clip_msaa16.png": {
       "allowed-digests": [
         [
           "bitmap-64bitMD5", 
-          17313899900380566045
+          14833041371169287873
         ]
       ], 
       "ignore-failure": true, 
       "reviewed-by-human": true
     }, 
     "convex_poly_clip_nvprmsaa4.png": {
       "allowed-digests": [
         [
           "bitmap-64bitMD5", 
           6376195695931688412
@@ skipping 14379 matching lines @@
       "allowed-digests": [
         [
           "bitmap-64bitMD5", 
           10030599291822810250
         ]
       ], 
       "reviewed-by-human": false
     }
   }
 }