Use last CRAN version of `altdoc` #1686

Job	Run time
macos-latest with pre-built binary (release)	35s
macos-latest (release)	7m 27s
windows-latest with pre-built binary (oldrel-1)	41s
windows-latest (devel)	18m 32s
windows-latest with pre-built binary (release)	31s
windows-latest (release)	26m 57s
windows-latest with pre-built binary (devel)	42s
ubuntu-latest (devel)	7m 13s
ubuntu-latest with pre-built binary (oldrel-1)	14s
ubuntu-latest (release)	4m 26s
ubuntu-latest with pre-built binary (release)	21s
ubuntu-latest (oldrel-1)	9m 57s
ubuntu-latest with pre-built binary (devel)	15s
macos-latest (release) full-features	8m 42s
windows-latest (release) full-features	27m 5s
ubuntu-latest (release) full-features	5m 7s
	1h 58m 45s

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