github actions: update recommended lowest supported Rust to 1.77 #110

Job	Run time
Check (aarch64-unknown-linux-gnu)	1m 30s
Lints	30s
Check (x86_64-unknown-linux-gnu)	1m 23s
yamllint	16s
dependencies	35s
Check (aarch64-linux-android)	1m 55s
Check (x86_64-unknown-linux-musl)	1m 28s
Check (aarch64-unknown-linux-musl)	1m 32s
	9m 9s

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