Remove android_clang_dbg from PRESUBMIT.py

Remove android_clang_dbg from PRESUBMIT.py

This bot is no longer in CQ and is subsumed by
android_clang_dbg_recipe.  It is a waste of resources to run two bots
by default.

Also, we are bringing up a replacement for android_clang_dbg_recipe
(see the linked bug), and this would allow us to recycle the shorter
bot name.

R=phajdan.jr@chromium.org
BUG=434516
TEST=git cl try: doesn't trigger android_clang_dbg

Committed: https://crrev.com/d138f04f43a4e1b7d22ba4b5b5c208a9a9de586c
Cr-Commit-Position: refs/heads/master@{#305460}

[Sergey Berezin, 2014-11-21 20:23:55]

PTAL

[Paweł Hajdan Jr., 2014-11-24 15:25:32]

LGTM

[Sergey Berezin, 2014-11-24 18:25:02]

The CQ bit was checked by sergeyberezin@chromium.org

[commit-bot: I haz the power, 2014-11-24 18:26:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/751613004/1

[commit-bot: I haz the power, 2014-11-24 19:08:03]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-24 19:08:39]

Patchset 1 (id:??) landed as
https://crrev.com/d138f04f43a4e1b7d22ba4b5b5c208a9a9de586c
Cr-Commit-Position: refs/heads/master@{#305460}