Fixed TOC entry for 2012 Service Pack release notes to match title

Author: Bruce Hamilton

docs/sql-server/TOC.md

@@ -22,7 +22,7 @@
 ## [SQL Server 2017 Notes](sql-server-2017-release-notes.md)
 ## [SQL Server 2016 Notes](sql-server-2016-release-notes.md)
 ## [SQL Server 2014 Notes](sql-server-2014-release-notes.md)
-## [SQL Server 2012 Release Notes](sql-server-2012-sp4-release-notes.md)
+## [SQL Server 2012 Service Pack release notes](sql-server-2012-sp4-release-notes.md)
 ## [SQL Server 2012 Notes](sql-server-2012-release-notes.md)
 ## [SQL Server 2008 R2 SP2 Notes](sql-server-2008-r2-sp2-release-notes.md)