Remove mention of returning data URLs from sync API #593

Job	Run time
build (20.x)	7s
test (node, 18.x)	25s
test (node, 20.x)	23s
test (node, 22.x)	29s
integration-deno (deno, v1.x)	7s
integration-edge (cloudflare-worker, 20.x)	21s
integration-browser (browser, chromium, 20.x)	31s
integration-bun (bun, 1.0.11)	12s
integration-nextjs (nextjs, 20.x)	28s
integration-browser (browser, firefox, 20.x)	5m 3s
integration-node (commonjs, 18.x)	8s
integration-browser (browser, webkit, 20.x)	47s
integration-node (commonjs, 20.x)	12s
integration-node (esm, 18.x)	12s
integration-node (esm, 20.x)	7s
integration-node (typescript, 18.x)	14s
integration-node (typescript, 20.x)	15s
	10m 1s

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