Update LICENSE to simplify copyright notice and remove RFN

LICENSE

@@ -1,13 +1,4 @@
-Copyright (c) 2014, Nikita Prokopov http://tonsky.me
-with Reserved Font Name Fira Code.
-
-Copyright (c) 2014, Mozilla Foundation https://mozilla.org/
-with Reserved Font Name Fira Sans.
-
-Copyright (c) 2014, Mozilla Foundation https://mozilla.org/
-with Reserved Font Name Fira Mono.
-
-Copyright (c) 2014, Telefonica S.A.
+Copyright (c) 2014, The Fira Code Project Authors (https://github.com/tonsky/FiraCode)
 
 This Font Software is licensed under the SIL Open Font License, Version 1.1.
 This license is copied below, and is also available with a FAQ at: