Remove unused Editor functions: insertOrderedList, insertUnorderedList, and commandIsSupportedFromMenuOrKeyBinding.

There are no callsites for them.  It was found by an internal tool.

BUG=none
TEST=none; no behavior changes.

Review URL: https://codereview.chromium.org/140493002

git-svn-id: svn://svn.chromium.org/blink/trunk@165188 bbb929c8-8fbe-4397-9dbb-9b2b20218538