Remove multi select usage (#6004)

As per title!

Also, I'm removing an incorrect logic in the enum migration runner that
takes care of the case where we have no defaultValue but non nullable
which is not a valid business case.

packages/twenty-front/src/modules/object-metadata/utils/formatFieldMetadataItemsAsFilterDefinitions.ts

@@ -22,7 +22,6 @@ export const formatFieldMetadataItemsAsFilterDefinitions = ({
         FieldMetadataType.Address,
         FieldMetadataType.Relation,
         FieldMetadataType.Select,
-        FieldMetadataType.MultiSelect,
         FieldMetadataType.Currency,
       ].includes(field.type)
     ) {