fix: scripts/signature-audits/requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-PYLINT-1089548
- https://snyk.io/vuln/SNYK-PYTHON-PYLINT-568073
- https://snyk.io/vuln/SNYK-PYTHON-PYLINT-609883
- https://snyk.io/vuln/SNYK-PYTHON-PYLINT-6514864
- https://snyk.io/vuln/SNYK-PYTHON-REQUESTS-6928867
- https://snyk.io/vuln/SNYK-PYTHON-SYMPY-6084333
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-7267250
- https://snyk.io/vuln/SNYK-PYTHON-ZIPP-7430899

scripts/signature-audits/requirements.txt

@@ -3,12 +3,15 @@ Click==7.0
 falcon==2.0.0
 hug==2.6.0
 isort==4.3.21
-pylint==2.4.3
+pylint==2.7.0
 pynamodb==4.0.0
 pytest==5.3.1
 python-dateutil==2.8.0
 oauthlib==3.1.0
-requests==2.31.0
+requests==2.32.2
 requests-oauthlib==1.2.0
 moto==1.3.14
 networkx>=2.6 # not directly required, pinned by Snyk to avoid a vulnerability
+sympy>=1.12 # not directly required, pinned by Snyk to avoid a vulnerability
+urllib3>=2.2.2 # not directly required, pinned by Snyk to avoid a vulnerability
+zipp>=3.19.1 # not directly required, pinned by Snyk to avoid a vulnerability