update copyrights

Author: tenox7

README.md

@@ -303,8 +303,7 @@ by default in unix stdio is buffered, you can work around it [in various ways](h
 ## legal stuff
 ```
 License: Apache 2.0
-Copyright (c) 2013-2018 Antoni Sawicki
-Copyright (c) 2019-2024 Google LLC
+Copyright (c) 2013-2025 Antoni Sawicki
 Copyright (c) 2023 Edgar Bonet
 Copyright (c) 2023 Sebastian Pipping
 ```

ttyplot.c

@@ -1,7 +1,6 @@
 //
 // ttyplot: a realtime plotting utility for terminal with data input from stdin
-// Copyright (c) 2018-2024 by Antoni Sawicki
-// Copyright (c) 2019-2023 by Google LLC
+// Copyright (c) 2018-2025 by Antoni Sawicki
 // Copyright (c) 2023-2024 by Edgar Bonet
 // Copyright (c) 2023-2024 by Sebastian Pipping
 // Apache License 2.0