Update pubgrub to 1447cf0 #2946

Job	Run time
windows (aarch64-pc-windows-msvc, x64)	1m 25s
windows (x86_64-pc-windows-msvc, x64)	1m 28s
windows (i686-pc-windows-msvc, x86)	1m 29s
macos-x86_64	1m 5s
linux-arm (aarch64-unknown-linux-gnu, aarch64, -e JEMALLOC_SYS_WITH_LG_PAGE=16)	1m 3s
linux-arm (armv7-unknown-linux-gnueabihf, armv7)	1m 3s
linux-arm (arm-unknown-linux-musleabihf, arm)	1m 0s
macos-aarch64	28s
sdist	3m 51s
linux (x86_64-unknown-linux-gnu, gcc)	1m 37s
linux (i686-unknown-linux-gnu, gcc -m32)	1m 39s
linux-powerpc (powerpc64le-unknown-linux-gnu, ppc64le, -e JEMALLOC_SYS_WITH_LG_PAGE=16)	1m 23s
linux-s390x (s390x-unknown-linux-gnu, s390x)	1m 16s
linux-powerpc (powerpc64-unknown-linux-gnu, ppc64, -e JEMALLOC_SYS_WITH_LG_PAGE=16)	1m 18s
linux-riscv64 (riscv64gc-unknown-linux-gnu, riscv64)	2m 24s
musllinux (x86_64-unknown-linux-musl)	1m 9s
musllinux-cross (armv7-unknown-linux-musleabihf, armv7)	1m 11s
musllinux (i686-unknown-linux-musl)	1m 6s
musllinux-cross (aarch64-unknown-linux-musl, aarch64, -e JEMALLOC_SYS_WITH_LG_PAGE=16)	1m 11s
	27m 6s

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