buffer: remove unused param from copyActual #3771

Job	Run time
Build slim tarball	2m 38s
x86_64-linux: with shared libraries	21m 31s
aarch64-darwin: with shared libraries	21m 52s
aarch64-linux: with shared libraries	18m 38s
x86_64-darwin: with shared libraries	27m 21s
	1h 32m 0s

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