Bump nltk from 3.5 to 3.6.6 in /link_guru

Bumps [nltk](https://github.com/nltk/nltk) from 3.5 to 3.6.6.
- [Release notes](https://github.com/nltk/nltk/releases)
- [Changelog](https://github.com/nltk/nltk/blob/develop/ChangeLog)
- [Commits](nltk/nltk@3.5...3.6.6)

---
updated-dependencies:
- dependency-name: nltk
  dependency-type: direct:production
...

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

link_guru/requirements.txt

@@ -27,7 +27,7 @@ more-itertools==8.2.0; python_version >= "3.5"
 mypy==0.770; python_version >= "3.5" and python_version < "3.8" or python_version >= "3.8"
 mypy-extensions==0.4.3; python_version >= "3.5" and python_version < "3.8" or python_version >= "3.8"
 -e git+https://github.com/pykancha/newspaper3k_wrapper.git@0bb55425d2ad93aff51a11aa209d9eabb0be0873#egg=newspaper3k-wrapper
-nltk==3.5
+nltk==3.6.6
 nodeenv==1.3.5
 packaging==20.3
 parse==1.15.0