chore: remove pflake8 version pin

[yanksyoon]

Applicable spec:

Overview

• Remove version pin

Rationale

Juju events changes

Module changes

Library changes

Checklist

• The charm style guide was applied
• The contributing guide was applied
• The changes are compliant with ISD054 - Managing Charm Complexity
• The documentation for charmhub is updated.
• The PR is tagged with appropriate label (urgent, trivial, complex)
• The docs/changelog is updated.

No user relevant changes

[github-actions]

Unused entries in .trivyignore

Image: ghcr.io/canonical/jenkins-agent-k8s:e444bef4e8c3ff3289f3d2a282be3aa105447fb1-_1.1_amd64

The following CVEs are in .trivyignore but not ignored by Trivy anymore:

• CVE-2023-45288
• CVE-2024-24790
• CVE-2024-34156
• CVE-2025-48734
• CVE-2024-45338
• CVE-2025-22874
• CVE-2025-47907