Remove HTML5 menu tag feature from experimental set

There are website compat issues with this feature on sites that use their
own <menuitem> tags (especially developer.apple.com).  Remove it from
the "experimental" set until there's a concrete plan in place to either
ship or resolve the issue to prevent ongoing issues for users running
with this flag enabled.

Note that you can always run chromium with
--enable-blink-features=ContextMenu in order to get this feature.

BUG=412945

Review-Url: https://codereview.chromium.org/2049093003
Cr-Commit-Position: refs/heads/master@{#398771}
1 file changed