Update plugin ksp to v1.9.21-1.0.16

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
com.google.devtools.ksp (source)	1.9.21-1.0.15 -> 1.9.21-1.0.16

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Release Notes

google/ksp (com.google.devtools.ksp)

### [`v1.9.21-1.0.16`](https://togithub.com/google/ksp/releases/tag/1.9.21-1.0.16) [Compare Source](https://togithub.com/google/ksp/compare/1.9.21-1.0.15...1.9.21-1.0.16) ##### Issue fixed [#​1653](https://togithub.com/google/ksp/issues/1653) KSP 1.9.21-1.0.15 leaking memory and causing OOMs

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Configuration

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