build(deps): bump urllib3 from 1.26.5 to 1.26.6

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.26.5 to 1.26.6.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/1.26.6/CHANGES.rst)
- [Commits](urllib3/urllib3@1.26.5...1.26.6)

---
updated-dependencies:
- dependency-name: urllib3
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

requirements-pinned.txt

@@ -7,4 +7,4 @@ pycparser==2.20           # via cffi
 pynacl==1.4.0             # via securesystemslib
 requests==2.25.1
 securesystemslib[crypto,pynacl]==0.20.1
-urllib3==1.26.5           # via requests
+urllib3==1.26.6           # via requests