Migrate license to AGPL.

gradle.properties

@@ -1,18 +1,8 @@
 #
-# Copyright (c) 2022 New Vector Ltd
-#
-# 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
-#
-#     http://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.
+# Copyright 2022 New Vector Ltd.
 #
+# SPDX-License-Identifier: AGPL-3.0-only
+# Please see LICENSE in the repository root for full details.
 
 # Project-wide Gradle settings.
 # IDE (e.g. Android Studio) users: