Update dependency pdm to v2.21.0

[RKIMetadataExchange]

This PR contains the following updates:

Package	Update	Change
pdm (changelog)	minor	==2.20.1 -> ==2.21.0

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Release Notes

pdm-project/pdm (pdm)

v2.21.0

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Features & Improvements

• Pass original working directory as env variable to pdm scripts (#​3179)
• Output similar commands or script command when the input command is not correct (#​3270)
• improve readability of Python interpreter validation message (#​3276)
• Print task name by default when using pdm run (#​3277)
• Make OrderedSet.__contains__ run in O(1) (#​3280)
• Emit post_lock after writing pyproject.toml and pdm.lock in add/update (#​3285)
• Drop support of Python 3.8 (#​3298)

Bug Fixes

• Fix the name normalization issue for optional dependency groups. (#​3271)
• Don't use uv when installing plugins in project. (#​3283)
• Fix the bug that pdm plugins are invalid after installation on ubuntu system python. (#​3289)

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