remove broken link to database directory

Since database is a submodule, the link no longer works and it
makes no sense here to link to prjtrellis-db.

Signed-off-by: Alexander Graf <alex@antistatix.de>

README.md

diff --git a/README.md b/README.md
index 0d159a4..7290727 100644
--- a/README.md
+++ b/README.md
@@ -146,7 +146,7 @@
 ### Database
 
 Running the all fuzzers in order will produce a database which documents the
-bitstream format in the [database](database) directory.
+bitstream format in the database directory.
 
 
 ## Credits