Rename license file

Tesseract uses the file LICENSE to show the Apache License,
so rename COPYING to LICENSE.

Signed-off-by: Stefan Weil <[email protected]>

Author: stweil

COPYING renamed to LICENSE

@@ -6,4 +6,4 @@ See the [Tesseract wiki](https://github.com/tesseract-ocr/tesseract/wiki/Data-Fi
 for additional information.
 
 All data in the repository are licensed under the
-Apache-2.0 License, see file [COPYING](COPYING).
+Apache-2.0 License, see file [LICENSE](LICENSE).