Bump urllib3 from 1.26.15 to 1.26.18 in /requirements

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.26.15 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@1.26.15...1.26.18)

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

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

Author: dependabot[bot]

requirements/docs.txt

@@ -5,7 +5,7 @@
 #    pip-compile --output-file=requirements/docs.txt --resolver=backtracking requirements/docs.in
 #
 ansi2html==1.8.0
-    # via -r requirements/docs.in
+    # via -r docs.in
 certifi==2023.7.22
     # via requests
 charset-normalizer==3.1.0
@@ -29,27 +29,27 @@ markdown==3.3.7
     #   mkdocs-material
     #   pymdown-extensions
 markdown-include==0.8.1
-    # via -r requirements/docs.in
+    # via -r docs.in
 markupsafe==2.1.2
     # via jinja2
 mergedeep==1.3.4
     # via mkdocs
 mkdocs==1.4.2
     # via
-    #   -r requirements/docs.in
+    #   -r docs.in
     #   mkdocs-exclude
     #   mkdocs-material
     #   mkdocs-simple-hooks
 mkdocs-exclude==1.0.2
-    # via -r requirements/docs.in
+    # via -r docs.in
 mkdocs-material==9.1.5
-    # via -r requirements/docs.in
+    # via -r docs.in
 mkdocs-material-extensions==1.1.1
     # via mkdocs-material
 mkdocs-simple-hooks==0.1.5
-    # via -r requirements/docs.in
+    # via -r docs.in
 numpy==1.24.2
-    # via -r requirements/docs.in
+    # via -r docs.in
 packaging==23.0
     # via mkdocs
 pygments==2.15.0
@@ -70,10 +70,10 @@ regex==2023.3.23
 requests==2.31.0
     # via mkdocs-material
 ruff==0.0.261
-    # via -r requirements/docs.in
+    # via -r docs.in
 six==1.16.0
     # via python-dateutil
-urllib3==1.26.15
+urllib3==1.26.18
     # via requests
 watchdog==3.0.0
     # via mkdocs