Bump version to v2.0.0-rc7 #283

Job	Run time
aarch64-unknown-linux-gnu	2m 58s
aarch64-unknown-linux-musl	3m 8s
x86_64-unknown-linux-gnu	1m 49s
x86_64-unknown-linux-musl	2m 59s
arm-unknown-linux-gnueabi	3m 10s
arm-unknown-linux-gnueabihf	3m 6s
armv7-unknown-linux-gnueabihf	3m 7s
powerpc-unknown-linux-gnu	2m 58s
powerpc64-unknown-linux-gnu	3m 1s
powerpc64le-unknown-linux-gnu	3m 36s
s390x-unknown-linux-gnu	3m 14s
aarch64-apple-darwin	2m 31s
x86_64-apple-darwin	2m 16s
x86_64-pc-windows-msvc	4m 51s
aarch64-pc-windows-msvc	4m 30s
publish	0s
	47m 14s

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