Bump boto3 in /sample-apps/python-manual-instrumentation-sample-app

Bumps [boto3](https://github.com/boto/boto3) from 1.26.160 to 1.28.1.
- [Release notes](https://github.com/boto/boto3/releases)
- [Changelog](https://github.com/boto/boto3/blob/develop/CHANGELOG.rst)
- [Commits](boto/boto3@1.26.160...1.28.1)

---
updated-dependencies:
- dependency-name: boto3
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

sample-apps/python-manual-instrumentation-sample-app/requirements.txt

@@ -1,4 +1,4 @@
-boto3==1.26.160
+boto3==1.28.1
 Flask==2.3.2
 opentelemetry-distro==0.39b0
 opentelemetry-exporter-otlp==1.18.0