CI: Disable fail-fast for main test job #4068

Job	Run time
Book tests	1m 37s
Bitrot check	1m 51s
Build target wasm32-unknown-unknown	1m 49s
Build target wasm32-wasi	1m 42s
Code coverage	3m 39s
Intra-doc links	1m 34s
Rustfmt	19s
Test on ubuntu-latest	7m 13s
Test on i686-unknown-linux-gnu	13m 24s
Test on windows-latest	11m 26s
Test on i686-unknown-linux-gnu with beta features	13m 28s
Test on macOS-latest	1m 57s
Test on ubuntu-latest with beta features	7m 24s
Test on i686-unknown-linux-gnu with nightly features	15m 58s
Test on windows-latest with beta features	11m 35s
Test on macOS-latest with beta features	1m 49s
Test on ubuntu-latest with nightly features	8m 21s
Test on windows-latest with nightly features	12m 22s
Test on macOS-latest with nightly features	2m 1s
	1h 59m 29s

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