Cover quotes for the `plain text` version

[DenBond7]

#2933 covered only the HTML version

We need to cover the plain text version like

Message-ID: <ZE3RJQg@mail.flowcrypt.test>
Subject: Re: quotes
To: Den <den@flowcrypt.test>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

Reply from Android

Regards,

Den at FlowCrypt

On 2025-02-20 at 13:13, Den<denbond7@flowcrypt.test> wrote:
rrr

=D1=87=D1=82, 20 =D0=BB=D1=8E=D1=82. 2025=E2=80=AF=D1=80. =D0=BE 13:12 De=
n at FlowCrypt <den@flowcrypt.test> =D0=BF=D0=B8=D1=88=D0=B5:
>
> Reply 1
>
>
> On Thu, Feb 20, 2025 at 1:10=E2=80=AFPM Den<denbond7@flowcrypt=
l.test> wrote:
> >
> > eee
> >
> > --
> > Regards,
> > Den
>
>
>
> --
> Regards,
> Den at FlowCrypt



--
Regards,
Den

for a separate PR

Originally posted by @DenBond7 in #2902