pw_toolchain: Remove "dummy" toolchain

Bug: 386
Change-Id: I3ba946ca66498aea75fe97bd67d29955c08bf477
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/46924
Pigweed-Auto-Submit: Rob Mohr <mohrr@google.com>
Reviewed-by: David Rogers <davidrogers@google.com>
Commit-Queue: Rob Mohr <mohrr@google.com>

pw_toolchain/dummy/BUILD.gn

diff --git a/pw_toolchain/dummy/BUILD.gn b/pw_toolchain/dummy/BUILD.gn
deleted file mode 100644
index a19f1d0..0000000
--- a/pw_toolchain/dummy/BUILD.gn
+++ /dev/null
@@ -1,22 +0,0 @@
-# Copyright 2021 The Pigweed Authors
-#
-# Licensed under the Apache License, Version 2.0 (the "License"); you may not
-# use this file except in compliance with the License. You may obtain a copy of
-# the License at
-#
-#     https://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
-# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
-# License for the specific language governing permissions and limitations under
-# the License.
-
-import("//build_overrides/pigweed.gni")
-
-import("$dir_pw_toolchain/non_c_toolchain.gni")
-
-# This toolchain has been DEPRECATED. Do not use it; use
-# "$dir_pw_toolchain/default:default" instead.
-pw_non_c_toolchain("dummy") {
-}