[obs] fix non-dmabuf 24-bit imports #2434

Job	Run time
host-windows-cross	39s
docs	42s
host-linux	39s
client (gcc, g++, xdg-shell, Release)	59s
module	27s
client (gcc, g++, xdg-shell, Debug)	1m 9s
host-windows-native	1m 19s
obs (gcc)	40s
client (gcc, g++, libdecor, Release)	52s
obs (clang)	44s
client (gcc, g++, libdecor, Debug)	42s
client (clang, clang++, xdg-shell, Release)	1m 7s
client (clang, clang++, xdg-shell, Debug)	55s
client (clang, clang++, libdecor, Release)	1m 15s
client (clang, clang++, libdecor, Debug)	59s
	13m 8s

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