account_invoice: Convert report into bytes before storing

account_invoice: Convert report into bytes before storing

If the invoice report has a text output, we must encode it as utf-8 before
storing it.
And we do not need to convert to bytes the data read because Binary field is
already doing that.

issue10937

[reviewbot, 2022-01-26 22:48:56]

checks OK
URL: https://codereview.tryton.org/376581002

[rietveld-bot_tryton.org, 2022-02-03 21:26:17]

New changeset a22984e8d532 by Cédric Krier in branch 'default':
Convert report into bytes before storing
https://hg.tryton.org/modules/account_invoice/rev/a22984e8d532

[rietveld-bot_tryton.org, 2022-02-03 21:26:23]

New changeset 58415c3abb6b by Cédric Krier in branch 'default':
Convert report into bytes before storing
https://hg.tryton.org/tryton-env/rev/58415c3abb6b

[rietveld-bot_tryton.org, 2022-02-07 22:34:58]

New changeset 59a2c5a5f428 by Cédric Krier in branch '6.2':
Convert report into bytes before storing
https://hg.tryton.org/modules/account_invoice/rev/59a2c5a5f428


New changeset 79aec7c017d8 by Cédric Krier in branch '6.0':
Convert report into bytes before storing
https://hg.tryton.org/modules/account_invoice/rev/79aec7c017d8


New changeset b548a46aeded by Cédric Krier in branch '5.0':
Convert report into bytes before storing
https://hg.tryton.org/modules/account_invoice/rev/b548a46aeded