Update autoroller after FromImpl was removed from depot tools

In https://chromium-review.googlesource.com/c/509693/ the From
keyword was removed. This update the script to match that (we
also were no longer using it).

BUG=libyuv:704
NOTRY=True

Change-Id: Iccbbfb426a3acd986fbc036672fb51abc2c5d346
Reviewed-on: https://chromium-review.googlesource.com/513908Reviewed-by: Frank Barchard <fbarchard@google.com>
Commit-Queue: Henrik Kjellander <kjellander@chromium.org>

tools_libyuv/autoroller/roll_deps.py

@@ -66,7 +66,6 @@ def ParseDepsDict(deps_content):
   local_scope = {}
   var = GClientKeywords.VarImpl({}, local_scope)
   global_scope = {
-    'From': GClientKeywords.FromImpl,
     'Var': var.Lookup,
     'deps_os': {},
   }