docs(blockstore): polish documentation on block limits #11652

Job	Run time
ledgers / ledger-replay	7m 15s
firedancer / firedancer-localnet	4m 24s
tests / test (linux_gcc_noarch64)	51s
tests / test (linux_gcc_x86_64)	8m 10s
tests / test (linux_gcc_icelake)	6m 27s
tests / test (linux_clang_x86_64)	6m 55s
tests / test (linux_clang_icelake)	6m 45s
tests / test (native)	4m 43s
tests / test (native-no-agave)	3m 16s
ledgers / ledger-coverage	0s
	48m 46s

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