build: Bump urllib3 from 1.26.8 to 1.26.18 in /docs

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.26.8 to 1.26.18.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/main/CHANGES.rst)
- [Commits](urllib3/urllib3@1.26.8...1.26.18)

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

Signed-off-by: dependabot[bot] <[email protected]>

docs/requirements.txt

@@ -19,11 +19,11 @@ click==8.0.3
 colorama==0.4.4
     # via sphinx-autobuild
 datetime==4.3
-    # via -r docs/requirements.in
+    # via -r requirements.in
 docutils==0.17.1
     # via sphinx
 furo==2022.1.2
-    # via -r docs/requirements.in
+    # via -r requirements.in
 idna==3.3
     # via requests
 imagesize==1.3.0
@@ -34,21 +34,21 @@ livereload==2.6.3
     # via sphinx-autobuild
 markupsafe==2.0.1
     # via
-    #   -r docs/requirements.in
+    #   -r requirements.in
     #   jinja2
 packaging==21.3
     # via sphinx
 pep517==0.12.0
     # via pip-tools
 pip-tools==6.4.0
-    # via -r docs/requirements.in
+    # via -r requirements.in
 pyenchant==3.2.2
     # via
-    #   -r docs/requirements.in
+    #   -r requirements.in
     #   sphinxcontrib-spelling
 pygments==2.11.2
     # via
-    #   -r docs/requirements.in
+    #   -r requirements.in
     #   furo
     #   sphinx
 pyparsing==3.0.7
@@ -67,12 +67,12 @@ soupsieve==2.3.1
     # via beautifulsoup4
 sphinx==4.4.0
     # via
-    #   -r docs/requirements.in
+    #   -r requirements.in
     #   furo
     #   sphinx-autobuild
     #   sphinxcontrib-spelling
 sphinx-autobuild==2021.3.14
-    # via -r docs/requirements.in
+    # via -r requirements.in
 sphinxcontrib-applehelp==1.0.2
     # via sphinx
 sphinxcontrib-devhelp==1.0.2
@@ -86,12 +86,12 @@ sphinxcontrib-qthelp==1.0.3
 sphinxcontrib-serializinghtml==1.1.5
     # via sphinx
 sphinxcontrib-spelling==7.3.2
-    # via -r docs/requirements.in
+    # via -r requirements.in
 tomli==2.0.0
     # via pep517
 tornado==6.1
     # via livereload
-urllib3==1.26.8
+urllib3==1.26.18
     # via requests
 wheel==0.38.1
     # via pip-tools