Bump signalfx from 1.1.15 to 1.1.16 in /tests

Bumps [signalfx](https://github.com/signalfx/signalfx-python) from 1.1.15 to 1.1.16.
- [Release notes](https://github.com/signalfx/signalfx-python/releases)
- [Changelog](https://github.com/signalfx/signalfx-python/blob/master/CHANGELOG.md)
- [Commits](signalfx/signalfx-python@v1.1.15...v1.1.16)

---
updated-dependencies:
- dependency-name: signalfx
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

tests/requirements.txt

@@ -20,6 +20,6 @@ redis==4.3.4
 requests==2.28.1
 sanic==21.6.2
 semver==2.13.0
-signalfx==1.1.15
+signalfx==1.1.16
 pika==1.3.1
 elasticsearch==7.13.4