Bump govuk_publishing_components from 35.19.0 to 35.21.4 #952

Job	Run time
Integration tests	1m 22s
Lint ERB / Lint ERB	29s
Lint JavaScript / Run Standardx	11s
Lint Ruby / Run RuboCop	27s
Lint SCSS / Run Stylelint	15s
Run Pact tests / Verify pact tests	37s
Security Analysis / Run Brakeman	23s
Test JavaScript / Run Jasmine	1m 10s
Test Ruby / Run RSpec	1m 15s
	6m 9s

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