rustup: update to 1.29.0 #67643

Job	Run time
Lint templates	39s
Build packages (x86_64-musl, x86_64-musl, musl, linux/amd64, 1)	8m 7s
Build packages (aarch64, x86_64, glibc, linux/amd64, 0)	6m 41s
Build packages (armv7l, x86_64, glibc, linux/amd64, 0)	5m 54s
Build packages (i686, i686, glibc, linux/386, 1)	7m 50s
Build packages (x86_64, x86_64, glibc, linux/amd64, 1)	7m 0s
Build packages (aarch64-musl, x86_64-musl, musl, linux/amd64, 0)	6m 37s
Build packages (armv6l-musl, x86_64-musl, musl, linux/amd64, 0)	1m 16s
	44m 4s

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