fix(docs): correctly state that bulk ops require subname

docs/dns/rrsets.rst

@@ -473,17 +473,15 @@ the process when some changes already have been applied.
 
 Field requirements
 ``````````````````
-In all cases, the ``subname`` field is optional.  If missing, the empty subname
-is assumed.
-
-For the ``POST`` and ``PUT`` methods, all other fields are required for each
-given RRset.  With ``POST``, only new RRsets are acceptable (i.e. the domain
-must not yet have an RRset with the same subname and type), while ``PUT``
-allows both creating new RRsets and modifying existing ones.
-
-For the ``PATCH`` method, only ``type`` is required; if you want to modify only
-``ttl`` or ``records``, you can skip the other field.  To create a new RRset
-using ``PATCH``, all fields but ``subname`` must be specified.
+For the ``POST`` and ``PUT`` methods, all fields are required for each given
+RRset.  With ``POST``, only new RRsets are acceptable (i.e. the domain must
+not yet have an RRset with the same subname and type), while ``PUT`` allows
+both creating new RRsets and modifying existing ones.
+
+For the ``PATCH`` method, only ``subname `` and ``type`` is required; if you
+want to modify only ``ttl`` or ``records``, you can skip the other field.  To
+create a new RRset using ``PATCH``, all fields but ``subname`` must be
+specified.
 
 To delete an RRset during a bulk operation, use ``PATCH`` or ``PUT`` and set
 ``records`` to ``[]``.