[DOCS] Revert fix for broken link

Author: lcawl

docs/reference/sql/language/index.asciidoc

@@ -7,7 +7,7 @@ This chapter describes the SQL semantics supported in X-Pack namely:
 
 <<sql-data-types>>:: Data types
 <<sql-commands>>:: Commands
-<<sql-index-pattern>>:: Index patterns
+<<sql-index-patterns>>:: Index patterns
 
 include::data-types.asciidoc[]
 include::syntax/index.asciidoc[]