Update 'required' status for new serializers

(cherry picked from commit 2306e29743eb25266c78bec5357d1194e0778c58)

InvenTree/part/serializers.py

@@ -47,7 +47,7 @@ class PartAttachmentSerializer(InvenTreeModelSerializer):
     Serializer for the PartAttachment class
     """
 
-    attachment = InvenTreeAttachmentSerializerField()
+    attachment = InvenTreeAttachmentSerializerField(required=True)
 
     class Meta:
         model = PartAttachment