Bug 1526659 - Use the default 3 chunks instead of 2 for Windows debug/ASan jsreftests to avoid time-outs. r=jmaher

Tests are imported from test262 upstream so this test suite is expected to become slower over time.

Differential Revision: https://phabricator.services.mozilla.com/D36295

--HG--
extra : moz-landing-system : lando

taskcluster/ci/test/reftest.yml

@@ -80,7 +80,8 @@ jsreftest:
         by-test-platform:
             android-hw.*\/debug: 12
             android-hw.*/(opt|pgo)?: 6
-            windows.*: 2
+            windows.*\/opt: 2
+            windows10-64-asan/opt: 3
             windows10-64-ccov/debug: 5
             linux64-ccov/.*: 5
             linux64-qr/opt: 4