docs: clarify that SSR is required for SSG with content #26947

Job	Run time
lint-all	1m 14s
pkg-pr-new	49s
test-kit-svelte-async (build)	1m 14s
test-kit (24, ubuntu-latest, chromium)	1m 13s
test-kit-server-side-route-resolution (build)	1m 13s
test-others (24)	1m 15s
test-kit-svelte-async (dev)	1m 14s
test-kit (20, ubuntu-latest, chromium)	1m 14s
test-kit-server-side-route-resolution (dev)	1m 13s
test-kit (22, ubuntu-latest, chromium)	1m 14s
test-kit (18, ubuntu-latest, chromium)	1m 13s
test-others (22)	1m 14s
test-others (20)	1m 13s
test-others (18)	1m 14s
test-kit-cross-browser (18, windows-latest, chromium, dev)	1m 5s
test-kit-cross-browser (18, ubuntu-latest, firefox, dev)	1m 14s
test-kit-cross-browser (18, macOS-latest, webkit, build)	1m 15s
test-kit-cross-browser (18, ubuntu-latest, firefox, build)	1m 14s
test-kit-cross-browser (18, windows-latest, chromium, build)	1m 5s
test-kit-cross-browser (18, macOS-latest, webkit, dev)	11s
	22m 51s

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