Also removes listing of targets in webrtc_fuzzers which is very prone to not being up to date. They're not required for ClusterFuzz integration or building locally. This also means that adding fuzzers won't require approval outside the fuzzers directory. BUG=webrtc:4771 R=kjellander@webrtc.org, stefan@webrtc.org Review URL: https://codereview.webrtc.org/1518973003 . Cr-Commit-Position: refs/heads/master@{#11067}