[deps] Update cryptography requirement from ~=42.0.2 to ~=42.0.8

Updates the requirements on [cryptography](https://github.com/pyca/cryptography) to permit the latest version.
- [Changelog](https://github.com/pyca/cryptography/blob/main/CHANGELOG.rst)
- [Commits](pyca/cryptography@42.0.2...42.0.8)

---
updated-dependencies:
- dependency-name: cryptography
  dependency-type: direct:production
...

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

requirements.txt

@@ -2,5 +2,5 @@
 django>=3.2.18,!=4.0.*,<4.3
 openwisp-utils @ https://github.com/openwisp/openwisp-utils/tarball/master
 jsonfield>=3.1.0,<4.0.0
-cryptography~=42.0.2
+cryptography~=42.0.8
 pyOpenSSL~=24.1.0