Update type-field.asciidoc
Fixed asciidoc syntax on deprecated annotation
[[mapping-type-field]]
=== `_type` field
-deprecated::[6.0.0,See <<removal-of-types>>]
+deprecated[6.0.0,See <<removal-of-types>>]
Each document indexed is associated with a <<mapping-type-field,`_type`>> (see
<<mapping-type>>) and an <<mapping-id-field,`_id`>>. The `_type` field is
