Bump pyyaml from 5.1.2 to 5.2 (#1150)

Bumps [pyyaml](https://github.com/yaml/pyyaml) from 5.1.2 to 5.2.
- [Release notes](https://github.com/yaml/pyyaml/releases)
- [Changelog](https://github.com/yaml/pyyaml/blob/5.2/CHANGES)
- [Commits](https://github.com/yaml/pyyaml/compare/5.1.2...5.2)

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

infra/spawn_pipeline_requirements.txt

@@ -1,4 +1,4 @@
 json-e==3.0.0
-pyyaml==5.1.2
+pyyaml==5.2
 requests==2.22.0
 taskcluster==24.0.0