docs: correct spec docs of fswap module #4503

Job	Run time
build (amd64, gcc)	1m 4s
build (arm64, aarch64-linux-gnu-gcc, g++-aarch64-linux-gnu)	1m 22s
cleanup-runs	8s
install-tparse	18s
split-test-files	19s
test-cosmovisor	2m 31s
test-race (00)	4m 17s
test-race (01)	2m 41s
tests (00)	3m 10s
test-race (02)	1m 48s
tests (01)	3m 32s
test-race (03)	2m 10s
tests (02)	2m 37s
tests (03)	3m 3s
upload-coverage-report	28s
	29m 28s

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