Remove un-used copy from building dockers (pytorch#18868)

The removed copy seems to be stale, it is never used.

Author: Erik-Lundell

.ci/docker/build.sh

@@ -1,6 +1,7 @@
 #!/bin/bash
 # Copyright (c) Meta Platforms, Inc. and affiliates.
 # All rights reserved.
+# Copyright 2026 Arm Limited and/or its affiliates.
 #
 # This source code is licensed under the BSD-style license found in the
 # LICENSE file in the root directory of this source tree.
@@ -94,11 +95,6 @@ BUILD_DOCS=1
 # Copy requirements-lintrunner.txt from root to here
 cp ../../requirements-lintrunner.txt ./
 
-# Copy arm setup script from root to here
-# TODO(huydhn): Figure out a way to rebuild the Docker image automatically
-# with a new image hash when the content here is updated
-cp -r ../../examples/arm/ ./arm
-
 docker build \
   --no-cache \
   --progress=plain \