Fix duplicate href warning in README

Author: elprans

README.rst

@@ -29,8 +29,7 @@ In our testing asyncpg is, on average, **2x** faster than psycopg2
 .. image:: performance.png
 
 The above results are a geometric mean of benchmarks obtained with PostgreSQL
-client driver benchmarking toolbench available
-`here <https://github.com/MagicStack/pgbench>`_.
+`client driver benchmarking toolbench <https://github.com/MagicStack/pgbench>`_.
 
 
 Features