Fix docs of the `_ignored` meta field.
Relates
@@ -48,9 +48,6 @@ can be customised when a mapping type is created.
All fields in the document which contain non-null values.
-[float]
-=== Indexing meta-fields
-
<<mapping-ignored-field,`_ignored`>>::
All fields in the document that have been ignored at index time because of
