Bullseye release date in Debian history

[sebul <sebuls@gmail.com>]

Hello.

https://salsa.debian.org/ddp-team/project-history/-/edit/master/project-history.en.dbk
says at Line 490
<para>
Debian 11 <emphasis>Bullseye</emphasis> (no release date yet): named for
Woody's wooden toyhorse that appeared in Toy Story 2.
</para>
</chapter>

At Line 1746
<section id="rel-11"><title>The 11.x Releases</title>
<para>
Debian 11.0 (<emphasis>Bullseye</emphasis>) was released August 14th, 2021.
</para>

Please update master/project-history.en.dbk file.