Bump waitress from 1.4.0 to 2.1.1

Bumps [waitress](https://github.com/Pylons/waitress) from 1.4.0 to 2.1.1.
- [Release notes](https://github.com/Pylons/waitress/releases)
- [Changelog](https://github.com/Pylons/waitress/blob/master/CHANGES.txt)
- [Commits](Pylons/waitress@v1.4.0...v2.1.1)

---
updated-dependencies:
- dependency-name: waitress
  dependency-type: direct:production
...

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

requirements.txt

@@ -3,7 +3,7 @@ SQLAlchemy>=1.3.0
 alembic==1.0.0
 pyramid_mako==1.0.2
 zope.sqlalchemy==1.0
-waitress==1.4.0
+waitress==2.1.1
 pastedeploy>=2.0
 paste>=2.0
 psycopg2-binary==2.8.4