build(deps): bump securesystemslib[crypto,pynacl] from 0.25.0 to 0.26.0

Bumps [securesystemslib[crypto,pynacl]](https://github.com/secure-systems-lab/securesystemslib) from 0.25.0 to 0.26.0.
- [Release notes](https://github.com/secure-systems-lab/securesystemslib/releases)
- [Changelog](https://github.com/secure-systems-lab/securesystemslib/blob/master/CHANGELOG.md)
- [Commits](secure-systems-lab/securesystemslib@v0.25.0...v0.26.0)

---
updated-dependencies:
- dependency-name: securesystemslib[crypto,pynacl]
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

requirements-pinned.txt

@@ -6,5 +6,5 @@ idna==3.4                 # via requests
 pycparser==2.21           # via cffi
 pynacl==1.5.0             # via securesystemslib
 requests==2.28.1
-securesystemslib[crypto,pynacl]==0.25.0
+securesystemslib[crypto,pynacl]==0.26.0
 urllib3==1.26.14           # via requests