fix: OTHERS/PDF_Downloader/requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-IDNA-6597975
- https://snyk.io/vuln/SNYK-PYTHON-REQUESTS-5595532
- https://snyk.io/vuln/SNYK-PYTHON-REQUESTS-6928867
- https://snyk.io/vuln/SNYK-PYTHON-REQUESTS-72435
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-1014645
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-1533435
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-174323
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-174464
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-5926907
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-5969479
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-6002459
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-7267250
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-72681

Author: snyk-bot

OTHERS/PDF_Downloader/requirements.txt

@@ -1,2 +1,4 @@
 beautifulsoup4==4.10.0
-requests==2.18.4
+requests==2.32.2
+idna>=3.7 # not directly required, pinned by Snyk to avoid a vulnerability
+urllib3>=1.26.19 # not directly required, pinned by Snyk to avoid a vulnerability