fix: requirements.txt to reduce vulnerabilities (openvinotoolkit#203)

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-SCIKITLEARN-1079100

Author: snyk-bot

requirements.txt

@@ -39,3 +39,4 @@ ipykernel==5.*
 pygments>=2.7.4 # not directly required, pinned by Snyk to avoid a vulnerability
 nltk>=3.6 # not directly required, pinned by Snyk to avoid a vulnerability
 rsa>=4.7 # not directly required, pinned by Snyk to avoid a vulnerability
+scikit-learn>=0.24.2 # not directly required, pinned by Snyk to avoid a vulnerability