Bump ujson from 5.5.0 to 5.6.0 in /python (#2602)

Bumps [ujson](https://github.com/ultrajson/ultrajson) from 5.5.0 to 5.6.0.
- [Release notes](https://github.com/ultrajson/ultrajson/releases)
- [Commits](ultrajson/ultrajson@5.5.0...5.6.0)

---
updated-dependencies:
- dependency-name: ujson
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

python/setup.py

@@ -9,7 +9,7 @@
     url="https://github.com/signalfx/signalfx-agent",
     packages=find_packages(),
     install_requires=[
-        'ujson==5.5.0',
+        'ujson==5.6.0',
     ],
     classifiers=[
         "Programming Language :: Python :: 3",