Remove explicit docsrs configuration flag from docs.rs metadata #180

Job	Run time
Cross (sparcv9-sun-solaris)	27s
Linux x32 (x86_64-unknown-linux-gnux32)	30s
Cross (x86_64-unknown-illumos)	31s
Tier 2 (x86_64-unknown-fuchsia)	17s
Apple Other	56s
Tier 2 (x86_64-unknown-redox)	9s
Tier 2 (x86_64-fortanix-unknown-sgx)	10s
Tier 3 (aarch64-kmc-solid_asp3)	23s
ESP-IDF	22s
No Atomics	10s
Tier 3 (aarch64-unknown-nto-qnx710)	21s
RDRAND (x86_64-unknown-uefi)	23s
RDRAND (x86_64-unknown-l4re-uclibc)	23s
Tier 3 (armv6k-nintendo-3ds)	22s
Web no_std	27s
Tier 3 (armv7-sony-vita-newlibeabihf)	20s
Web no_std with Atomics	28s
Tier 3 (i686-unknown-hurd-gnu)	22s
RNDR	14s
Web	31s
Web with Atomics	33s
Tier 3 (x86_64-unknown-hermit)	23s
WasmV1 no_std	30s
Tier 3 (x86_64-wrs-vxworks)	20s
WasmV1 no_std with Atomics	30s
Tier 3 (x86_64-unknown-dragonfly)	21s
Tier 3 (x86_64-unknown-haiku)	25s
	10m 48s

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