Delete an unused (manual) workflow, added missing copyright headers. (#162050)

Just TLC while working on something related.

Author: matanlurey

.github/workflows/files-changed.yml

@@ -1,3 +1,7 @@
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
 name: Generate Changed Files JSON
 
 on:

.github/workflows/lock.yaml

@@ -1,3 +1,7 @@
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
 # Configuration for Lock Threads - https://github.com/dessant/lock-threads
 
 name: 'Lock Threads'

.github/workflows/minimal.yml

@@ -1,3 +1,7 @@
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
 name: No Response
 
 # Both `issue_comment` and `scheduled` event types are required for this Action