[CQ] Remove obsolete sign-cla check

The check moved to gerrit.

NOTRY=true
TBR=sergiyb@chromium.org

Bug: chromium:851737
Change-Id: I1db1f320bb1c71c8abbce29ef545cbd70ff4d168
Reviewed-on: https://chromium-review.googlesource.com/1099382Reviewed-by: Sergiy Byelozyorov <sergiyb@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53715}

infra/config/cq.cfg

@@ -111,7 +111,5 @@ verifiers {
       }
     }
   }
-
-  sign_cla {}
 }