fix(sec): upgrade nltk to 3.6.6

[pen4]

What happened？

There are 1 security vulnerabilities found in nltk 3.4.5

• MPS-2022-15003

What did I do？

Upgrade nltk from 3.4.5 to 3.6.6 for vulnerability fix

What did you expect to happen？

Ideally, no insecure libs should be used.

The specification of the pull request

PR Specification from OSCS

Signed-off-by:pen4[email protected]