Remove docsrs cfg_attributes #491

Job	Run time
Cross (aarch64-unknown-linux-gnu)	2m 4s
Cross (i686-unknown-linux-gnu)	2m 38s
Cross (x86_64-pc-windows-gnu)	2m 26s
Cross (x86_64-unknown-linux-gnu)	2m 18s
Cross (aarch64-unknown-linux-musl)	2m 30s
Cross (arm-unknown-linux-gnueabi)	2m 37s
Cross (arm-unknown-linux-gnueabihf)	2m 24s
Cross (armv7-unknown-linux-gnueabihf)	1m 47s
Cross (mips-unknown-linux-gnu)	2m 2s
Cross (mips64-unknown-linux-gnuabi64)	2m 16s
Cross (mips64el-unknown-linux-gnuabi64)	2m 6s
Cross (mipsel-unknown-linux-gnu)	2m 11s
Cross (powerpc-unknown-linux-gnu)	2m 20s
Cross (powerpc64le-unknown-linux-gnu)	1m 59s
Cross (riscv64gc-unknown-linux-gnu)	2m 25s
Cross (s390x-unknown-linux-gnu)	2m 3s
Cross (x86_64-unknown-linux-musl)	2m 25s
	38m 31s

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