Revert of Add Widevine signature files into Mac build

third_party/widevine/cdm/widevine.gni

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 declare_args() {
   # Allow widevinecdmadapter to be built in Chromium.
   enable_widevine = false
 }
-
-template("widevine_sign_file") {
-  # For official builds, generate a signature file for |file| which will
-  # be used by Widevine. If |signature_file| is not specified, the signature
-  # file will be in the same directory as |file|.
-  action(target_name) {
-    forward_variables_from(invoker,
-                           [
-                             "file",
-                             "signature_file",
-                             "deps",
-                           ])
-    assert(defined(file), "File to be signed must be specified.")
-    if (!defined(signature_file)) {
-      signature_file = "$file.sig"
-    }
-
-    script = "//third_party/widevine/scripts/signature_generator.py"
-    sources = [
-      "$file",
-    ]
-    outputs = [
-      "$signature_file",
-    ]
-    args = [
-      "--input_file",
-      rebase_path("$file", root_build_dir),
-      "--output_file",
-      rebase_path("$signature_file", root_build_dir),
-    ]
-  }
-}