chore(deps): update external/libexpat digest to 624da0f #81

Job	Run time
lib_android (monero)	25m 46s
lib_android (wownero)	24m 10s
lib_darwin (monero)	13m 52s
ios build (monero)	13m 28s
lib_darwin (wownero)	13m 50s
ios build (wownero)	13m 49s
lib_linux (monero)	2m 50s
lib_linux (wownero)	2m 38s
macos build (monero)	3m 50s
lib_mingw (monero)	3m 41s
macos build (wownero)	3m 55s
lib_mingw (wownero)	3m 19s
lib_sailfishos_aarch64 (monero)	3m 44s
lib_sailfishos_i486 (monero)	2m 47s
lib_sailfishos_aarch64 (wownero)	3m 20s
lib_sailfishos_i486 (wownero)	2m 0s
wallet_cake_android	20m 38s
wallet_xmruw_android (monero)	7m 14s
wallet_xmruw_android (wownero)	7m 37s
comment on pr	3s
	2h 52m 31s

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