Remove unused libjingle_xmpphelp target.

NOTRY=true

Review-Url: https://codereview.webrtc.org/2011503002
Cr-Original-Commit-Position: refs/heads/master@{#12877}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 1b32acdbd01c28bf02fecff84992aa30c252677e
4 files changed