Update link to LICENSE in COPYING.md (#865)

The link to the license was outdated and resulted in a broken path. The correct filename is "LICENSE.txt".

Co-authored-by: Geometrically <[email protected]>

COPYING.md

@@ -1,6 +1,6 @@
 # Copying
 
-The source code of the labrinth repository is licensed under the GNU Affero General Public License, Version 3 only, which is provided in the file [LICENSE](./LICENSE). However, some files listed below are licensed under a different license.
+The source code of the labrinth repository is licensed under the GNU Affero General Public License, Version 3 only, which is provided in the file [LICENSE](./LICENSE.txt). However, some files listed below are licensed under a different license.
 
 ## Modrinth logo
 
@@ -11,4 +11,4 @@ Any files depicting the Modrinth branding, including the wrench-in-labyrinth log
 This includes, but may not be limited to, the following files:
 
 - assets/logo.svg
-- assets/favicon.ico
+- assets/favicon.ico