Try to switch to a regular ubuntu repo instead of using azure mirror … #428

Job	Run time
Book tests	1m 21s
Bitrot check	1m 34s
Build target wasm32-unknown-unknown	1m 48s
Intra-doc links	1m 27s
Build target wasm32-wasi	1m 39s
Rustfmt	15s
Test on ubuntu-latest	7m 17s
Test on i686-unknown-linux-gnu	13m 13s
Test on windows-latest	10m 44s
Test on i686-unknown-linux-gnu with beta features	13m 53s
Test on macOS-latest	5m 52s
Test on i686-unknown-linux-gnu with nightly features	15m 11s
Test on ubuntu-latest with beta features	7m 18s
Test on windows-latest with beta features	11m 5s
Test on macOS-latest with beta features	5m 56s
Test on ubuntu-latest with nightly features	8m 8s
Test on windows-latest with nightly features	12m 4s
Test on macOS-latest with nightly features	6m 16s
	2h 5m 1s

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