md5

Only run CI on latest commit of PR branches. #1112

Job	Run time
set-msrv / set-msrv	6s
minimal-versions / minimal-versions	42s
test (stable)	43s
test (1.85.0)	35s
build (stable, wasm32-unknown-unknown)	14s
build (1.85.0, loongarch64-unknown-linux-gnu)	26s
build (1.85.0, thumbv7em-none-eabi)	30s
build (1.85.0, wasm32-unknown-unknown)	24s
build (stable, thumbv7em-none-eabi)	22s
build (stable, loongarch64-unknown-linux-gnu)	28s
	4m 30s

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