Update dependency plugin_platform_interface to v2.1.7

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
plugin_platform_interface (source)	dependencies	patch	2.1.6 -> 2.1.7

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Release Notes

flutter/packages (plugin_platform_interface)

v2.1.7

Compare Source

• Changes MockPlatformInterfaceMixin to a mixin class for better
  compatibility with projects that have a minumum Dart SDK version of 3.0.
• Updates minimum supported SDK version to Dart 3.0.

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