build(deps): bump cffi from 1.15.0 to 1.15.1

Bumps [cffi](http://cffi.readthedocs.org) from 1.15.0 to 1.15.1.

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

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

Author: dependabot[bot]

requirements-pinned.txt

@@ -1,5 +1,5 @@
 certifi==2022.6.15        # via requests
-cffi==1.15.0              # via cryptography, pynacl
+cffi==1.15.1              # via cryptography, pynacl
 charset-normalizer==2.1.0 # via requests
 cryptography==37.0.3      # via securesystemslib
 idna==3.3                 # via requests