Update dependency towncrier to v25

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
towncrier	24.8.0 → 25.8.0

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Release Notes

twisted/towncrier (towncrier)

v25.8.0: Towncrier 25.8.0

Compare Source

towncrier 25.8.0 (2025-08-30)

Features

• Support was added for Mercurial SCM. (#&#8203;394 <https://github.com/twisted/towncrier/issues/394>_)
• The towncrier check command now has a --staged flag to inspect the files staged for commit when checking for a news fragment: useful in a pre-commit hook (#&#8203;676 <https://github.com/twisted/towncrier/issues/676>_)
• When used with an pyproject.toml file, when no explicit values are
  defined for [tool.towncrier.name|package] they will now fallback to
  the value of [project.name]. (#&#8203;687 <https://github.com/twisted/towncrier/issues/687>_)
• More simple configuration for Keep a Changelog style changelogs (#&#8203;691 <https://github.com/twisted/towncrier/issues/691>_)
• Added support for Python 3.13 and removed support for Python 3.8. (#&#8203;700 <https://github.com/twisted/towncrier/issues/700>_)

Bugfixes

• Multi-line newsfragments that ends with a code block will now have a newline inserted before appending the link to the issue, to avoid breaking formatting. (#&#8203;614 <https://github.com/twisted/towncrier/issues/614>_)
• Markdown header level is correctly inferred from title_format. (#&#8203;695 <https://github.com/twisted/towncrier/issues/695>_)

Improved Documentation

• The documentation RST source files are now included in the sdist package. (#&#8203;672 <https://github.com/twisted/towncrier/issues/672>_)
• Refactor the default markdown template to make it easier to understand, extend, and customize. (#&#8203;706 <https://github.com/twisted/towncrier/issues/706>_)

Deprecations and Removals

• When no sections are present,
  the default Markdown template now renders the category headers as H2.
  In previous versions it was rendered as H3. (#&#8203;663 <https://github.com/twisted/towncrier/issues/663>_)

Misc

• #&#8203;667 <https://github.com/twisted/towncrier/issues/667>, #&#8203;669 <https://github.com/twisted/towncrier/issues/669>, #&#8203;679 <https://github.com/twisted/towncrier/issues/679>, #&#8203;680 <https://github.com/twisted/towncrier/issues/680>, #&#8203;682 <https://github.com/twisted/towncrier/issues/682>, #&#8203;701 <https://github.com/twisted/towncrier/issues/701>, #&#8203;702 <https://github.com/twisted/towncrier/issues/702>, #&#8203;713 <https://github.com/twisted/towncrier/issues/713>

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