fix: samples/server/petstore/python-aiohttp-srclayout/test-requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-AIOHTTP-8383923

Author: snyk-bot

samples/server/petstore/python-aiohttp-srclayout/test-requirements.txt

@@ -2,3 +2,4 @@ pytest~=7.1.0
 pytest-cov>=2.8.1
 pytest-randomly>=1.2.3
 pytest-aiohttp>=0.3.0
+aiohttp>=3.10.11 # not directly required, pinned by Snyk to avoid a vulnerability