Always get actual size in CopyObjectPart (#12466)
Always get actual size in CopyObjectPart (#12466)

Always use `GetActualSize` to get the part size, not just when encrypted.

Fixes mint test io.minio.MinioClient.uploadPartCopy, 
error "Range specified is not valid for source object".
donatello/minio,NitishT/minio,balamurugana/minio,vadmeste/minio,NitishT/minio,minio/minio,krisis/minio,NitishT/minio,NitishT/minio,balamurugana/minio,krisis/minio,donatello/minio,vadmeste/minio,minio/minio