Bump waitress from 1.4.2 to 1.4.3 in /src

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] <[email protected]>

Author: dependabot[bot]

src/requirements.txt

@@ -1,4 +1,4 @@
-waitress==1.4.2
+waitress==1.4.3
 flask==1.1.1
 prometheus_client==0.7.1
 pygelf==0.3.6