Also remove --if-needed from clang update in DEPS.

Bug: libyuv:816, libyuv:814
Test: bots still build and local GN build works

Change-Id: I91998b8eee1b0cbe344f02a9369a1bbc45cb0140
Reviewed-on: https://chromium-review.googlesource.com/1204790Reviewed-by: Nico Weber <thakis@chromium.org>