Update node to v20 (major) - autoclosed #2353

Job	Run time
Static analysis	1m 30s
Dependencies, Unit tests (16)	1m 31s
Dependencies, Unit tests (18)	1m 33s
Dependencies, Unit tests (20)	1m 28s
Build application (govuk-docs)	2m 10s
Build application (govuk-template)	1m 35s
Build libraries	2m 0s
Test application (govuk-docs, chromium)	1m 20s
Test application (govuk-docs, firefox)	1m 23s
Test application (govuk-docs, electron)	1m 12s
Test application (govuk-template, chromium)	1m 31s
Test application (govuk-template, firefox)	1m 22s
Test application (govuk-template, electron)	1m 12s
	19m 47s

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