Bump postorius from 1.3.10 to 1.3.13 in /web

Bumps [postorius](https://gitlab.com/mailman/postorius) from 1.3.10 to 1.3.13.
- [Release notes](https://gitlab.com/mailman/postorius/tags)
- [Commits](https://gitlab.com/mailman/postorius/compare/v1.3.10...v1.3.13)

---
updated-dependencies:
- dependency-name: postorius
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

web/requirements.txt

@@ -1,4 +1,4 @@
 mailmanclient==3.3.5
-postorius==1.3.10
+postorius==1.3.13
 hyperkitty==1.3.11
 django-mailman3==1.3.15