Add note about updating search index after release #8782

Job	Run time
Go Lint	1m 59s
Rego PR checks	13s
Generate Code	1m 27s
Check Generated	11s
Go compat build/test (ubuntu-22.04, 1.19)	12s
Go compat build/test (macos-latest, 1.19)	1s
Go Test (linux)	5s
Go Test (darwin)	1s
Go Build (linux amd64)	6s
Go Build (linux arm64)	5s
Go Build (windows)	5s
Go Build (darwin)	2s
Go Race Detector	5s
WASM	4s
smoke-test-binaries	1s
docker image smoke test	1s
	4m 38s

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