Bump actions/deploy-pages from 2 to 3 #293

Job	Run time
apt-based	44s
nix-flake-checks	55s
nix-based (with-nixpkgs)	1m 30s
docker-based (alpine, deploy-image)	4m 13s
nix-based (with-opam-nix)	1m 53s
docker-based (archlinux)	4m 35s
opam-based (ubuntu, 4.11.x)	8m 52s
docker-based (centos, no-tests)	3m 43s
opam-based (ubuntu, 4.11.x, lower-bounds, no-doc)	9m 3s
docker-based (debian)	4m 12s
opam-based (ubuntu, 4.12.x)	8m 51s
docker-based (debian-testing)	4m 24s
opam-based (ubuntu, 4.13.x)	8m 38s
docker-based (debian-unstable)	4m 13s
opam-based (ubuntu, 4.14.x, lower-bounds, no-doc)	9m 55s
docker-based (fedora)	4m 34s
opam-based (ubuntu, 4.14.x, deploy-doc)	9m 13s
docker-based (opensuse)	4m 36s
opam-based (ubuntu, 4.14.1, bytecode)	9m 54s
docker-based (oraclelinux)	4m 41s
opam-based (macos, 4.14.x)	16m 49s
docker-based (ubuntu)	4m 17s
opam-based (windows, 4.14.x, no-tests)	14m 19s
opam-based (ubuntu, 5.0.x)	9m 24s
docker-based (ubuntu-lts)	4m 9s
	2h 37m 37s

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