fix: samples/server/petstore/python-fastapi/requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-JINJA2-8548181
- https://snyk.io/vuln/SNYK-PYTHON-JINJA2-8548987

Author: snyk-bot

samples/server/petstore/python-fastapi/requirements.txt

@@ -16,7 +16,7 @@ httptools>=0.3.0,<0.7.0
 httpx==0.24.1
 idna==3.7
 itsdangerous==1.1.0
-Jinja2==3.1.4
+Jinja2==3.1.5
 MarkupSafe==2.0.1
 orjson==3.9.15
 promise==2.3