docs: add missing 2.12 upgrade page to nav menu #34647

Job	Run time
changes	13s
changes	13s
Check changes to generated code	6m 7s
Check changes to generated code	6m 7s
Build & cache Go code	2m 57s
Build & cache Go code	2m 57s
Build, test & lint UI code	2m 12s
Build, test & lint UI code	2m 12s
Ensure Go modules synchronicity	37s
Ensure Go modules synchronicity	37s
Lint Go code	4m 8s
Lint Go code	4m 8s
Run unit tests with -race for Go packages	8m 4s
Run unit tests with -race for Go packages	8m 4s
Run end-to-end tests (v1.29.1, true)	46m 51s
Run end-to-end tests (v1.29.1, true)	46m 51s
Run unit tests for Go packages	4m 53s
Run unit tests for Go packages	4m 53s
Run end-to-end tests (v1.28.6, false)	44m 12s
Run end-to-end tests (v1.28.6, false)	13m 27s
Run end-to-end tests (v1.27.10, false)	50m 50s
Run end-to-end tests (v1.27.10, false)	50m 50s
Run end-to-end tests (v1.26.13, false)	52m 50s
Run end-to-end tests (v1.26.13, false)	52m 50s
E2E Tests - Composite result	1s
E2E Tests - Composite result	1s
Process & analyze test artifacts	0s
Process & analyze test artifacts	0s
	6h 57m 5s

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