[numeric-separator] Enable test262 tests

Bug: v8:7317
Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: I2920abc732b9006a24fcf11edb6bb779ac627d5a
Reviewed-on: https://chromium-review.googlesource.com/961064Reviewed-by: Mathias Bynens <mathias@chromium.org>
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51946}

test/test262/testcfg.py

@@ -50,11 +50,11 @@ FEATURE_FLAGS = {
   'class-fields-public': '--harmony-public-fields',
   'optional-catch-binding': '--harmony-optional-catch-binding',
   'class-fields-private': '--harmony-private-fields',
+  'numeric-separator-literal': '--harmony-numeric-separator',
 }
 
 SKIPPED_FEATURES = set(['Array.prototype.flatten',
-                        'Array.prototype.flatMap',
-                        'numeric-separator-literal'])
+                        'Array.prototype.flatMap'])
 
 DATA = os.path.join(os.path.dirname(os.path.abspath(__file__)), "data")
 ARCHIVE = DATA + ".tar"