Doc: update ubuntu ppa #773

Job	Run time
Linux build test (gcc, g++, ON)	1m 8s
Linux build test (gcc, g++, OFF)	1m 10s
FreeBSD-amd64	7m 37s
Linux build test (clang, clang++, ON)	1m 13s
Linux-amd64	3m 24s
Linux build test (clang, clang++, OFF)	57s
Linux-old-amd64	3m 38s
Linux-aarch64	10m 33s
Linux build test (musl-gcc, musl-g++, OFF)	59s
macOS-universal	11m 11s
spellcheck	11s
Windows-amd64	2m 22s
Windows-i686	6m 40s
Release	0s
	51m 3s

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