Update pyyaml requirement from <5.4 to <6.1

Updates the requirements on [pyyaml](https://github.com/yaml/pyyaml) to permit the latest version.
- [Changelog](https://github.com/yaml/pyyaml/blob/main/CHANGES)
- [Commits](yaml/pyyaml@3.01...6.0.1)

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

Signed-off-by: dependabot[bot] <[email protected]>

constraints.txt

@@ -1 +1 @@
-pyyaml<5.4
+pyyaml<6.1