Try running journey tests on macOS as well as Ubuntu #518

Job	Run time
pure-rust-build	1m 57s
test-fast (windows-latest)	15m 20s
test	10m 1s
test-fast (macos-latest)	4m 14s
test-fast (ubuntu-latest)	3m 53s
cargo-deny	30s
cargo-deny-advisories	29s
lint	4m 0s
test-32bit	5m 33s
test-32bit-cross (armv7-linux-androideabi)	1m 2s
test-fixtures-windows	14m 51s
check-blocking	2s
check-packetline (ubuntu-latest)	7s
test-journey (ubuntu-latest)	3m 45s
test-journey (macos-latest)	7m 0s
WebAssembly (wasm32-unknown-unknown)	1m 6s
WebAssembly (wasm32-wasi)	52s
Tests pass	1s
	1h 14m 43s

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