Feature Policy: update virtual test flags

FeaturePolicyForPermissions has been retired from runtime enabled
features. We don't need to mention it in VirtualTestSuites.

BUG=788390

Change-Id: I22e05513852fcc17c2eea514fd5c54b3c0051b37
Reviewed-on: https://chromium-review.googlesource.com/1176882Reviewed-by: Becca Hughes <beccahughes@chromium.org>
Commit-Queue: Eric Willigers <ericwilligers@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583832}

third_party/WebKit/LayoutTests/VirtualTestSuites

@@ -140,8 +140,7 @@
   {
     "prefix": "feature-policy-permissions",
     "base": "external/wpt/mediacapture-streams",
-    "args": ["--enable-features=UseFeaturePolicyForPermissions",
-             "--use-fake-device-for-media-stream",
+    "args": ["--use-fake-device-for-media-stream",
              "--use-fake-ui-for-media-stream"]
   },
   {