license: Strip copyright notice from LICENSE; update the one in README

This makes the whole LICENSE file an exact copy of the license,
which helps some software recognize that this is indeed the
Apache 2.0 license.  In particular, the `licensee` gem, which
is what GitHub uses to identify what license to display.

There's already a copyright notice in the README.
Update that, while we're here.

Author: gnprice

Diff for: LICENSE

@@ -1,23 +1,3 @@
-Copyright 2016-2018 Kandra Labs, Inc., and contributors
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this software 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.
-
-The software includes some works released by third parties under other
-free and open source licenses. Those works are redistributed under the
-license terms under which the works were received. For more details,
-see the ``docs/THIRDPARTY`` file included with this distribution.
-
---------------------------------------------------------------------------------
 
                                  Apache License
                            Version 2.0, January 2004

Diff for: README.md

@@ -85,7 +85,7 @@ Zulip Mobile supersedes two legacy Zulip apps,
 
 ## License
 
-Copyright (c) 2016-2018 Kandra Labs, Inc., and contributors, and 2016 Dropbox, Inc.
+Copyright (c) 2016-2022 Kandra Labs, Inc., and contributors, and 2016 Dropbox, Inc.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.