Remove dead Scaling SQL link

dd618e26 · Donne Martin · 419f29a8 · dd618e26
Commit dd618e26 authored Mar 07, 2017 by Donne Martin
--- a/README.md
+++ b/README.md
@@ -121,7 +121,6 @@ Review the [Contributing Guidelines](https://github.com/donnemartin/system-desig
    * [Service discovery](#service-discovery)
 * [Database](#database)
    * [Relational database management system (RDBMS)](#relational-database-management-system-rdbms)
-    * [Scaling SQL](#scaling-sql)
        * [Master-slave replication](#master-slave-replication)
        * [Federation](#federation)
        * [Sharding](#sharding)