Update updating_clang.md
Update updating_clang.md

android_clang_dbg_recipe now lives on the tryserver.chromium.android
master.

BUG=none
TBR=hans@chromium.org

Review URL: https://codereview.chromium.org/1544093002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#366782}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk