deps: Upgrade `freetype-sys` to version 0.21 #215

Job	Run time
stable, iOS, static library	36s
stable, Linux, shared library	21s
stable, Linux, static linking, no pkg-config	1m 36s
stable, macOS, shared library	31s
stable, macOS, static library	46s
stable, Emscripten, static library	1m 26s
stable, Windows, static library	1m 12s
Result	0s
	6m 28s

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