Bump lxml from 4.6.3 to 4.9.1 in /link_guru

Bumps [lxml](https://github.com/lxml/lxml) from 4.6.3 to 4.9.1.
- [Release notes](https://github.com/lxml/lxml/releases)
- [Changelog](https://github.com/lxml/lxml/blob/master/CHANGES.txt)
- [Commits](lxml/lxml@lxml-4.6.3...lxml-4.9.1)

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

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

link_guru/requirements.txt

@@ -22,7 +22,7 @@ importlib-metadata==1.6.0; python_version < "3.8" or python_version >= "3.5" and
 importlib-resources==1.5.0; python_version < "3.7"
 jieba3k==0.35.1
 joblib==0.14.1
-lxml==4.6.3
+lxml==4.9.1
 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"