chore(deps): update external/libexpat digest to 99b6fde #111

Job	Run time
lib_android (monero)	25m 6s
lib_android (wownero)	24m 41s
lib_darwin (monero)	13m 48s
ios build (monero)	1m 56s
lib_darwin (wownero)	13m 42s
ios build (wownero)	2m 0s
lib_linux (monero)	29m 57s
macos build (monero)	4m 55s
lib_linux (wownero)	28m 51s
macos build (wownero)	3m 48s
lib_mingw (monero)	3m 46s
lib_mingw (wownero)	3m 11s
lib_sailfishos_aarch64 (monero)	3m 12s
lib_sailfishos_i486 (monero)	2m 13s
lib_sailfishos_aarch64 (wownero)	3m 12s
lib_sailfishos_i486 (wownero)	2m 16s
wallet_cake_android	21m 33s
wallet_xmruw_android (monero)	1m 14s
wallet_xmruw_android (wownero)	1m 7s
test ts library	1m 7s
create single release file	0s
comment on pr	0s
	3h 11m 35s

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