Prepare for 1.6.0-M3 release #898

Job	Run time
linting (stable)	56s
features (--no-default-features)	1m 48s
linting (beta)	53s
features (--no-default-features --features serialization)	1m 44s
documentation	3m 50s
test (ubuntu-latest, stable)	1m 32s
features (--no-default-features --features serial)	1m 49s
test (ubuntu-latest, beta)	1m 34s
features (--no-default-features --features tls)	2m 2s
test (windows-latest, stable)	3m 38s
bindings-linux (x86_64-unknown-linux-gnu)	2m 27s
bindings-macos (x86_64-apple-darwin)	2m 15s
test (windows-latest, beta)	3m 7s
bindings-linux (i686-unknown-linux-gnu)	2m 29s
bindings-linux (x86_64-unknown-linux-musl)	2m 47s
bindings-windows (x86_64-pc-windows-msvc, true)	7m 5s
bindings-linux (arm-unknown-linux-gnueabihf)	2m 43s
bindings-windows (i686-pc-windows-msvc, false)	4m 16s
conformance	11m 7s
guide	1m 11s
bindings-linux (arm-unknown-linux-musleabihf)	2m 37s
bindings-linux (aarch64-unknown-linux-gnu)	2m 37s
bindings-linux (aarch64-unknown-linux-musl)	2m 40s
bindings-linux (armv7-unknown-linux-gnueabihf)	2m 37s
bindings-linux (arm-unknown-linux-gnueabi)	2m 40s
packaging	4m 18s
release	0s
	1h 16m 42s

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