chore(docs): mention rules_multirun #1550

Job	Run time
matrix-prep-os	1s
matrix-prep-bazelversion	4s
test (ubuntu-latest, 7.1.1, ., true)	4m 11s
test (ubuntu-latest, 7.1.1, ., false)	2m 14s
test (ubuntu-latest, 7.1.1, e2e/wasm, false)	4m 12s
test (ubuntu-latest, 7.1.1, e2e/smoke, true)	2m 27s
test (ubuntu-latest, 7.1.1, e2e/smoke, false)	14s
test (ubuntu-latest, 7.1.1, e2e/assertion, true)	4m 11s
test (ubuntu-latest, 6.4.0, ., true)	4m 10s
test (ubuntu-latest, 6.4.0, ., false)	12s
test (ubuntu-latest, 6.4.0, e2e/wasm, false)	2m 49s
test (ubuntu-latest, 6.4.0, e2e/smoke, true)	12s
test (ubuntu-latest, 6.4.0, e2e/smoke, false)	2m 25s
test (ubuntu-latest, 6.4.0, e2e/assertion, true)	4m 12s
test (macos-13, 7.1.1, ., true)	4m 2s
test (macos-13, 7.1.1, ., false)	4m 0s
test (macos-13, 7.1.1, e2e/smoke, true)	42s
test (macos-13, 7.1.1, e2e/smoke, false)	2m 54s
	43m 12s

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