DOC: removed Axis.subaxis from api doc (closes #1051)

It should actually be a private method. This is only a stop-gap measure until proper deprecation in larray 0.35 (see #1062)

Author: gdementen

doc/source/api.rst

@@ -62,7 +62,6 @@ Modifying/Selecting
    Axis.i
    Axis.by
    Axis.rename
-   Axis.subaxis
    Axis.extend
    Axis.insert
    Axis.replace