[dxwg] Remove note in section 6.3 (#1441)

agreiner has just created a new issue for https://github.com/w3c/dxwg:

== Remove note in section 6.3 ==
Note in section 6.3 seems to be left over from DCAT 2.


Please view or discuss this issue at https://github.com/w3c/dxwg/issues/1441 using your GitHub account


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