revert changes

Author: mofterdinger

db/common.cds

@@ -1,5 +1,4 @@
 namespace my.bookshop;
-using {sap.attachments.Attachments} from `com.sap.cds/cds-feature-attachments`;
 
 ////////////////////////////////////////////////////////////////////////////
 //
@@ -9,7 +8,3 @@ type TechnicalBooleanFlag : Boolean @(
     UI.Hidden,
     Core.Computed
 );
-
-// annotate Attachments with {
-//     modifiedAt @(odata.etag: null);
-// }