update_engine: Remove presubmit check for header_guard

Because of the revert crrev.com/c/1111797, header_guard doesn't
support the root param anymore, so presubmit is failing for
multiple files.

BUG=None
TEST='chromium/tools/depot_tools/cpplint.py src/aosp/system/update_engine/**/*.h'

Change-Id: Ie609378b947402fed8a09b1ee9085f50019266f4
Reviewed-on: https://chromium-review.googlesource.com/1128894
Commit-Ready: Márton Hunyady <[email protected]>
Tested-by: Márton Hunyady <[email protected]>
Reviewed-by: Amin Hassani <[email protected]>

Author: Marton Hunyady

CPPLINT.cfg

@@ -1,7 +1,4 @@
 # This should be kept in sync with platform2/CPPLINT.cfg
 set noparent
 
-# Header guard should start with UPDATE_ENGINE_
-root=..
-
-filter=-build/include_order,+build/include_alpha
+filter=-build/include_order,+build/include_alpha,-build/header_guard