Remove WebAudio doppler effect API surface (already no-ops)

Intent to Deprecate:
https://groups.google.com/a/chromium.org/d/msg/blink-dev/-1SI1GoHYO8/6XUjRs-fdv4J
Intent to Remove: https://groups.google.com/a/chromium.org/d/msg/blink-dev/59cVGPqud1M/gR8yby0_BgAJ
Feature: https://www.chromestatus.com/features/5753252045914112

BUG=439644
TEST=

patch from issue 2356223002 at patchset 20001 (http://crrev.com/2356223002#ps20001)

Review-Url: https://codereview.chromium.org/2380183002
Cr-Commit-Position: refs/heads/master@{#423915}
13 files changed