Update dependency mkdocs-material to v9.1.8

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
mkdocs-material	==9.1.6 -> ==9.1.8

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Release Notes

squidfunk/mkdocs-material

v9.1.8: mkdocs-material-9.1.8

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• Fixed #​5417: Theme breaks when palette is not defined (9.1.7 regression)

v9.1.7: mkdocs-material-9.1.7

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• Updated Persian (Farsi) and Turkish translations
• Fixed #​5401: Added missing flag to disable built-in tags plugin
• Fixed #​5206: Ensure defaults are set for primary and accent colors
• Fixed unnecessary inclusion of palette CSS when unused

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