FindBackward.cmake: restore original copyright

a typo in the copyright replace script caused the removal

cmake/modules/FindBackward.cmake

@@ -1,22 +1,24 @@
 #
-# Copyright 2013-2021 Software Radio Systems Limited
+# BackwardMacros.cmake
+# Copyright 2013 Google Inc. All Rights Reserved.
 #
-# This file is part of srsLTE
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
 #
-# srsLTE is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Affero General Public License as
-# published by the Free Software Foundation, either version 3 of
-# the License, or (at your option) any later version.
-#
-# srsLTE is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-# GNU Affero General Public License for more details.
-#
-# A copy of the GNU Affero General Public License can be found in
-# the LICENSE file in the top-level directory of this distribution
-# and at http://www.gnu.org/licenses/.
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
 #
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
 
 ###############################################################################
 # OPTIONS