CDB3-4257 Fix definition of scope "documentOf" for awards documents

https://procedure-dev.prozorro.sale/api/procedures/6440ec5746aef90078fa2ac9

AR:
There is possibility to upload award documents with scope - ['announcement', 'large_announcement', 'asset', 'large_asset', 'auction', 'bid', 'award', 'contract', 'cancellation', 'prolongation']

ER:
scope 'award' only

Also fix error message without privatization artefacts