docs: remove AUTHORS file

We haven't managed to keep this at all up to date, which defeats the
purpose. Please refer to the git history for a complete list of
contributors.

 AUTHORS | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/AUTHORS b/AUTHORS
deleted file mode 100644
index 6a84e17..0000000
--- a/AUTHORS
+++ /dev/null
@@ -1,6 +0,0 @@
-The following developers have contributed code to river:
- Isaac Freund
- Leon Henrik Plickat
- Marten Ringwelski
- Rishabh Das
- Bonicgamer