fix: engines/arachni/requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-JINJA2-9292516

Author: snyk-bot

engines/arachni/requirements.txt

@@ -10,7 +10,7 @@ greenlet==0.4.15
 gunicorn==20.0.4
 idna==2.5
 itsdangerous
-Jinja2==3.1.2
+Jinja2==3.1.6
 MarkupSafe==2.1.1
 more-itertools==4.3.0
 pathlib2==2.3.2