scripts: Update copyright in ext revision gen

Change-Id: I326142c2d3bcefda354b4be5aedb1cab496e0c27
diff --git a/scripts/external_revision_generator.py b/scripts/external_revision_generator.py
index e863dde..a4869ad 100644
--- a/scripts/external_revision_generator.py
+++ b/scripts/external_revision_generator.py
@@ -1,9 +1,9 @@
 #!/usr/bin/env python3
 #
-# Copyright (c) 2015-2019 The Khronos Group Inc.
-# Copyright (c) 2015-2019 Valve Corporation
-# Copyright (c) 2015-2019 LunarG, Inc.
-# Copyright (c) 2015-2019 Google Inc.
+# Copyright (c) 2015-2021 The Khronos Group Inc.
+# Copyright (c) 2015-2021 Valve Corporation
+# Copyright (c) 2015-2021 LunarG, Inc.
+# Copyright (c) 2015-2021 Google Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -38,10 +38,10 @@
         copyright += '\n'
         copyright += '/***************************************************************************\n'
         copyright += ' *\n'
-        copyright += ' * Copyright (c) 2015-2020 The Khronos Group Inc.\n'
-        copyright += ' * Copyright (c) 2015-2020 Valve Corporation\n'
-        copyright += ' * Copyright (c) 2015-2020 LunarG, Inc.\n'
-        copyright += ' * Copyright (c) 2015-2020 Google Inc.\n'
+        copyright += ' * Copyright (c) 2015-2021 The Khronos Group Inc.\n'
+        copyright += ' * Copyright (c) 2015-2021 Valve Corporation\n'
+        copyright += ' * Copyright (c) 2015-2021 LunarG, Inc.\n'
+        copyright += ' * Copyright (c) 2015-2021 Google Inc.\n'
         copyright += ' *\n'
         copyright += ' * Licensed under the Apache License, Version 2.0 (the "License");\n'
         copyright += ' * you may not use this file except in compliance with the License.\n'