Bump nltk in /NLP/Conversational-Recommendation-BASELINE

Bumps [nltk](https://github.com/nltk/nltk) from 3.4 to 3.4.5.
- [Release notes](https://github.com/nltk/nltk/releases)
- [Changelog](https://github.com/nltk/nltk/blob/develop/ChangeLog)
- [Commits](nltk/nltk@3.4...3.4.5)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

NLP/Conversational-Recommendation-BASELINE/requirements.txt

@@ -21,7 +21,7 @@ jieba==0.42.1
 jmespath==0.9.5
 kiwisolver==1.1.0
 matplotlib==2.2.3
-nltk==3.4
+nltk==3.4.5
 numpy==1.16.1
 objgraph==3.4.1
 opencv-python==4.1.1.26