Bad definition of `primaryMeasure`

[hoehrmann]

In https://github.com/sdmx-twg/sdmx-json/blob/71fe5eaa9fcd29e3c15f2f0216a19b9b650b1dbd/data-message/docs/1-sdmx-json-field-guide.md#attribute-relationship it says »primaryMeasure - String optional. Deprecated value having the same meaning than the relationship observation. For backward-compatibility only.« This rather confused me and looking at https://github.com/sdmx-twg/sdmx-json/issues/90 this seems mistaken. This should refer to the measures relationship.

(In doubt, please handle this as a public review comment on SDMX 3.1 once the comment period begins.)