Update validate-pyproject requirement from <0.16 to <0.21

[dependabot]

Updates the requirements on validate-pyproject to permit the latest version.

Release notes

Sourced from validate-pyproject's releases.

v0.20.2

Attempt to solve problems with release pipeline (CI), related to actions/upload-artifact#618. The package code is unchanged regarding v0.20.

Full Changelog: abravalheri/validate-pyproject@v0.20.1...v0.20.2

Changelog

Sourced from validate-pyproject's changelog.

========= Changelog

.. Development Version

Version 0.20

• setuptools plugin:
  • Update setuptools.schema.json, #206

Maintenance and Minor Changes

• Fix misplaced comments on formats.py, #184
• Adopt --import-mode=importlib for pytest to prevent errors with importlib.metadata, #203
• Update CI configs, #195 #202, #204, #205

Version 0.19

• Relax requirements about module names to also allow dash characters, #164
• Migrate metadata to pyproject.toml , #192

Version 0.18

• Allow overwriting schemas referring to the same tool, #175

Version 0.17

• Update version regex according to latest packaging version, #153
• Remove duplicate # ruff: noqa, #158
• Remove invalid top-of-the-file # type: ignore statement, #159
• Align tool.setuptools.dynamic.optional-dependencies with project.optional-dependencies, #170
• Bump min Python version to 3.8, #167

Version 0.16

• Fix setuptools readme field , #116
• Fix oneOf <> anyOf in setuptools schema, #117
• Add previously omitted type keywords for string values, #117
• Add schema validator check, #118
• Add SchemaStore conversion script, #119
• Allow tool(s) to be specified via URL (added CLI option: --tool), #121
• Support uint formats (as used by Ruff's schema), #128
• Allow schemas to be loaded from SchemaStore (added CLI option: --store), #133

Version 0.15

... (truncated)

Commits

• 435e09f Prevent Github action for ignoring files for cache
• c23edc4 Ensure iterator is consumed in tools/cache_urls_for_tests
• 6d0e71d Update CHANGELOG
• 18b3595 Update setuptools.schema.json (#206)
• d1ea8f3 Add tests to setuptools ext-modules
• f0c2f49 Update setuptools.schema.json
• 6a9d2ed Attempt building and linting in a single task for Cirrus CI (#205)
• 730e339 [pre-commit.ci] pre-commit autoupdate (#199)
• 538dab7 Update Cirrus CI config from latest PyScaffold template (#204)
• 0f0e464 Update Cirrus CI config from latest PyScaffold template
• Additional commits viewable in compare view

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