chore(docs): mention rules_multirun #1551

Job	Run time
matrix-prep-os	1s
matrix-prep-bazelversion	3s
test (ubuntu-latest, 7.1.1, ., true)	2m 21s
test (ubuntu-latest, 7.1.1, ., false)	5m 15s
test (ubuntu-latest, 7.1.1, e2e/wasm, false)	4m 19s
test (ubuntu-latest, 7.1.1, e2e/smoke, true)	24s
test (ubuntu-latest, 7.1.1, e2e/smoke, false)	2m 26s
test (ubuntu-latest, 7.1.1, e2e/assertion, true)	4m 39s
test (ubuntu-latest, 6.4.0, ., true)	5m 44s
test (ubuntu-latest, 6.4.0, ., false)	36s
test (ubuntu-latest, 6.4.0, e2e/wasm, false)	2m 41s
test (ubuntu-latest, 6.4.0, e2e/smoke, true)	26s
test (ubuntu-latest, 6.4.0, e2e/smoke, false)	2m 25s
test (ubuntu-latest, 6.4.0, e2e/assertion, true)	5m 0s
test (macos-13, 7.1.1, ., true)	6m 16s
test (macos-13, 7.1.1, ., false)	3m 52s
test (macos-13, 7.1.1, e2e/smoke, true)	2m 49s
test (macos-13, 7.1.1, e2e/smoke, false)	39s
	49m 56s

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