Update dependency towncrier to v26

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
towncrier	==25.8.0 → ==26.9.0

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Release Notes

twisted/towncrier (towncrier)

v26.9.0: Towncrier 26.9.0

Compare Source

Features

• towncrier build now support setting the date via the SOURCE_DATE_EPOCH specification. This adds support for Reproducible Builds. (#&#8203;746 <https://github.com/twisted/towncrier/issues/746>_)
• Wrapped line length can now be configured by setting wrap to an integer value greater than 0, using 79 by default if set to true. (#&#8203;464 <https://github.com/twisted/towncrier/issues/464>_)
• The towncrier create command line tool now has the --sub-issue option that is used when creating multiple fragments for the same issue number. (#&#8203;714 <https://github.com/twisted/towncrier/issues/714>_)

Bugfixes

• towncrier create now rejects fragment names whose issue identifier contains .. (#&#8203;733 <https://github.com/twisted/towncrier/issues/733>_)

Misc

• #&#8203;719 <https://github.com/twisted/towncrier/issues/719>, #&#8203;729 <https://github.com/twisted/towncrier/issues/729>, #&#8203;736 <https://github.com/twisted/towncrier/issues/736>, #&#8203;741 <https://github.com/twisted/towncrier/issues/741>, #&#8203;747 <https://github.com/twisted/towncrier/issues/747>_

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