Update url for old SDL2_ttf version used by CI #603

Job	Run time
linux-oldest	2m 44s
linux-per-backend	4m 29s
linux	5m 9s
linux-latest-dev	3m 20s
windows-sfml-sdl	1m 41s
windows-oldest	5m 42s
windows-static-mt	4m 54s
android-sdl	5m 13s
android-sfml-graphics	2m 3s
windows-clang	5m 12s
macos	5m 27s
ios-sdl	5m 14s
ios-sfml-graphics	1m 1s
nightly-build-windows-visual-studio	6m 59s
	59m 8s

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