build(deps): update pygal requirement from >=3.0.3 to >=3.1.0

[dependabot]

Updates the requirements on pygal to permit the latest version.

Release notes

Sourced from pygal's releases.

3.1.0

Added

• Add reverse_direction Gauge config parameter in Kozea/pygal#576

Fixed

• Fix lint
• Add read the docs yaml config
• Various clean up and update

Full Changelog: Kozea/pygal@3.0.5...3.1.0

Changelog

Sourced from pygal's changelog.

3.1.0

Fixed

• Lint
• Readthedocs config
• README and docs information

Added

• reverse_direction option for gauge

3.0.5

Fixed

• Remove test from setup.py

3.0.4

Fixed

• Missing declaration of importlib_metadata dependency in setup.py

3.0.3

Fixed

• Failure with tox due to missing README.md

3.0.2

Fixed

• Misused entry_points causing failure with Python 3.12

Changed

• Prevent installing with Python versions < 3.8
• Replace unmaintained pytest-flake8 with plain flake8

3.0.1

... (truncated)

Commits

• df20193 Bump 3.1.0
• 23d0463 Merge branch 'gauge-reverse-direction'
• 8c4ec19 Add reverse_direction Gauge config parameter
• 721a587 Merge pull request #575 from Kozea/cleanup-20251128
• d386d6e Update build status badges and links
• 73bf14e Remove duplicate README file
• b93c4c4 Update copyright year
• d1efc8c Update changelog
• 8c9d2a0 Update author info
• 6ae7129 Fix minimal python version in docs
• Additional commits viewable in compare view