[chromium][cast_runner] Remove unused prebuilt package rules

These rules now live in //src/{chromium,cast} in fuchsia.git and
these copies are no longer referenced anywhere.

Bug: 38900
Change-Id: I9c558bab12a339cfc3adef79e09a516da235567a
diff --git a/runtime/cast_runner/BUILD.gn b/runtime/cast_runner/BUILD.gn
deleted file mode 100644
index ac59796..0000000
--- a/runtime/cast_runner/BUILD.gn
+++ /dev/null
@@ -1,10 +0,0 @@
-# Copyright 2019 The Fuchsia Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-import("//build/packages/prebuilt_package.gni")
-
-prebuilt_package("cast_runner") {
-  archive = "//topaz/third_party/cast_runner/arch/$target_cpu/cast_runner.far"
-  visibility = [ "//src/cast:cast_runner" ]
-}
diff --git a/runtime/chromium/BUILD.gn b/runtime/chromium/BUILD.gn
deleted file mode 100644
index 46e0b07..0000000
--- a/runtime/chromium/BUILD.gn
+++ /dev/null
@@ -1,32 +0,0 @@
-# Copyright 2018 The Fuchsia Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-import("//build/packages/prebuilt_package.gni")
-import("//build/packages/prebuilt_test_manifest.gni")
-
-prebuilt_package("chromium") {
-  archive = "//topaz/third_party/chromium/arch/$target_cpu/chromium.far"
-  visibility = [ "//src/chromium:web_engine" ]
-}
-
-prebuilt_package("web_runner") {
-  archive = "//topaz/third_party/chromium/arch/$target_cpu/web_runner.far"
-  visibility = [ "//src/chromium:web_runner" ]
-}
-
-# Prebuilt FAR tests
-test_env = [
-  {
-    dimensions = {
-      device_type = "Intel NUC Kit NUC7i5DNHE"
-    }
-  },
-]
-
-prebuilt_test_manifest("chromium_tests") {
-  archive_dir = "//prebuilt/third_party/chromium_tests/arch/x64"
-  package_name_prefix = "chromium_tests"
-  environments = test_env
-  visibility = [ "//src/chromium:chromium_tests" ]
-}