Bump waitress from 1.4.2 to 1.4.3 (#571)

Bumps [waitress](https://github.com/Pylons/waitress) from 1.4.2 to 1.4.3.
- [Release notes](https://github.com/Pylons/waitress/releases)
- [Changelog](https://github.com/Pylons/waitress/blob/master/CHANGES.txt)
- [Commits](Pylons/waitress@v1.4.2...v1.4.3)

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

requirements.txt

@@ -65,7 +65,7 @@ translationstring==1.3
 Unidecode==1.1.1
 usersettings==1.0.7
 venusian==3.0.0
-waitress==1.4.2
+waitress==1.4.3
 webencodings==0.5.1
 WebOb==1.8.6
 zope.component==4.6