build(deps): bump cffi from 1.15.1 to 1.16.0

Bumps [cffi](https://github.com/python-cffi/cffi) from 1.15.1 to 1.16.0.
- [Release notes](https://github.com/python-cffi/cffi/releases)
- [Commits](python-cffi/cffi@v1.15.1...v1.16.0)

---
updated-dependencies:
- dependency-name: cffi
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

requirements/pinned.txt

@@ -1,5 +1,5 @@
 certifi==2023.7.22        # via requests
-cffi==1.15.1              # via cryptography, pynacl
+cffi==1.16.0              # via cryptography, pynacl
 charset-normalizer==3.3.0 # via requests
 cryptography==41.0.4      # via securesystemslib
 idna==3.4                 # via requests