Bug#976301: Fix invalid `changelog` format example

[Sean Whitton <spwhitton@spwhitton.name>]

control: tag -1 + moreinfo

Dear Anatoli,

On Thu 03 Dec 2020 at 05:08AM +03, Anatoli Babenia wrote:

> diff --git a/policy/ch-source.rst b/policy/ch-source.rst
> index edae8c1..1265c5e 100644
> --- a/policy/ch-source.rst
> +++ b/policy/ch-source.rst
> @@ -126,7 +126,7 @@ That format is a series of entries like this:
>       [blank line(s), included in output of dpkg-parsechangelog]
>       * even more change details
>       [optional blank line(s), stripped]
>     [----]{+[space]--+} maintainer name <email address>[two [-spaces]
> date-]{+spaces]date+}

I do not believe that what is already there is invalid or unclear.

Please explain your motivations.

-- 
Sean Whitton