Update index-document.asciidoc (#851)

Author: dam-bal

.doc/tab-widgets/index-document.asciidoc

@@ -18,7 +18,7 @@ client.Index("my_index", bytes.NewReader(data))
 
 // tag::fully-typed[]
 
-This is a simple way of indexing a documen by using the fully-typed API:
+This is a simple way of indexing a document by using the fully-typed API:
 
 [source,go]
 ----
@@ -33,4 +33,4 @@ typedClient.Index("my_index").
 		Do(context.TODO())
 ----
 
-// end::fully-typed[]
+// end::fully-typed[]