Fix link to LibFuzzer

CLA: trivial
Reviewed-by: NKurt Roeckx <kurt@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1801)

fuzz/README.md

@@ -3,7 +3,7 @@
 LibFuzzer
 =========
 
-Or, how to fuzz OpenSSL with [libfuzzer](llvm.org/docs/LibFuzzer.html).
+Or, how to fuzz OpenSSL with [libfuzzer](http://llvm.org/docs/LibFuzzer.html).
 
 Starting from a vanilla+OpenSSH server Ubuntu install.