fix(deps): update ngrx monorepo to v20 (major)

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
@ngrx/operators	^19.1.0 -> ^20.0.0
@ngrx/signals	19.1.0 -> 20.0.0

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Release Notes

ngrx/platform (@​ngrx/operators)

v20.0.0

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Bug Fixes

• www: Make API Pages Responsive (#​4885) (7f09858), closes #​4816

v19.2.1

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Bug Fixes

• signals: add current state as second argument of case reducer (#​4800) (95dbbfa)
• signals: expose WritableStateSource to withFeature callback (#​4792) (afb6528), closes #​4766

v19.2.0

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Features

• eslint-plugin: add schematic support for flat configs (#​4747) (f966d0a)
• signals: add Events plugin (#​4769) (980cf6f), closes #​4580

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