Bump urllib3 from 1.26.4 to 1.26.5 in /docs (#39)

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.26.4 to 1.26.5.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/main/CHANGES.rst)
- [Commits](urllib3/urllib3@1.26.4...1.26.5)

---
updated-dependencies:
- dependency-name: urllib3
  dependency-type: indirect
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

docs/requirements.txt

@@ -1,17 +1,17 @@
 -i https://pypi.org/simple/
 alabaster==0.7.12
-babel==2.9.0
-certifi==2020.12.5
+babel==2.9.1
+certifi==2021.5.30
 chardet==4.0.0
 commonmark==0.9.1
-docutils==0.16
+docutils==0.17.1
 flask-sphinx-themes==1.0.2
 idna==2.10
 imagesize==1.2.0
-jinja2==2.11.3
-markupsafe==1.1.1
+jinja2==3.0.1
+markupsafe==2.0.1
 packaging==20.9
-pygments==2.8.1
+pygments==2.9.0
 pyparsing==2.4.7
 pytz==2021.1
 recommonmark==0.6.0
@@ -20,8 +20,8 @@ snowballstemmer==2.1.0
 sphinx==3.2.1
 sphinxcontrib-applehelp==1.0.2
 sphinxcontrib-devhelp==1.0.2
-sphinxcontrib-htmlhelp==1.0.3
+sphinxcontrib-htmlhelp==2.0.0
 sphinxcontrib-jsmath==1.0.1
 sphinxcontrib-qthelp==1.0.3
-sphinxcontrib-serializinghtml==1.1.4
-urllib3==1.26.4
+sphinxcontrib-serializinghtml==1.1.5
+urllib3==1.26.5