Remove old libevent 2.1.5-beta tarball

Change-Id: I392f719da8dba36e5806e60b5d6f21b7e2684c83
diff --git a/libevent-2.1.5-beta.tar.gz b/libevent-2.1.5-beta.tar.gz
deleted file mode 100644
index fb89f2f..0000000
--- a/libevent-2.1.5-beta.tar.gz
+++ /dev/null
Binary files differ