Do not set Content-Length header to data response

Since version 0.8 werkzeug set the header automatically by default.

Closes #14010
(grafted from 5d2842d92f356a260afaa974ab5a413031505e95)

--HG--
branch : 7.0

trytond/trytond/ir/routes.py

@@ -270,7 +270,6 @@ def data(request, pool, model):
         response = Response(data, mimetype='text/csv; charset=' + encoding)
         response.headers.add(
             'Content-Disposition', 'attachment', filename=filename)
-        response.headers.add('Content-Length', len(data))
         return response