Allow Qt 5.3 msvc2013 opengl release buid failures

The previous commit (9ee8e0e)
accidentally allowed the wrong (64-bit) build to fail, whereas this
change allows the 32-bit build to fail instead (issue #61).

.appveyor.yml

@@ -15,7 +15,7 @@ environment:
 
 matrix:
   allow_failures:
-    - QTDIR: C:\Qt\5.3\msvc2013_64_opengl
+    - QTDIR: C:\Qt\5.3\msvc2013_opengl
       configuration: release
 
 configuration: