Bump dulwich from 0.19.16 to 0.20.5

Bumps [dulwich](https://github.com/dulwich/dulwich) from 0.19.16 to 0.20.5.
- [Release notes](https://github.com/dulwich/dulwich/releases)
- [Changelog](https://github.com/dulwich/dulwich/blob/master/NEWS)
- [Commits](jelmer/dulwich@dulwich-0.19.16...dulwich-0.20.5)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

requirements.txt

@@ -2,7 +2,7 @@ bump2version
 colorama >=0.4.3
 configupdater
 domdf-python-tools >=0.4.1
-dulwich==0.19.16
+dulwich==0.20.5
 importlib_resources
 jinja2 >=2.11.2
 packaging >=20.4