docs: fix python-redis link markup (apache#1683)

docs/installation.rst

@@ -224,7 +224,7 @@ Flask-Cache supports multiple caching backends (Redis, Memcached,
 SimpleCache (in-memory), or the local filesystem). If you are going to use
 Memcached please use the pylibmc client library as python-memcached does
 not handle storing binary data correctly. If you use Redis, please install
-[python-redis](https://pypi.python.org/pypi/redis).
+`python-redis <https://pypi.python.org/pypi/redis>`.
 
 For setting your timeouts, this is done in the Superset metadata and goes
 up the "timeout searchpath", from your slice configuration, to your