Bump actions/deploy-pages from 2 to 4 #296

Job	Run time
apt-based	49s
nix-flake-checks	49s
nix-based (with-nixpkgs)	1m 29s
docker-based (alpine, deploy-image)	4m 11s
nix-based (with-opam-nix)	1m 54s
opam-based (ubuntu, 4.11.x)	7m 37s
opam-based (ubuntu, 4.11.x, lower-bounds, no-doc)	9m 11s
docker-based (archlinux)	3m 7s
docker-based (centos, no-tests)	3m 36s
opam-based (ubuntu, 4.12.x)	7m 30s
docker-based (debian)	4m 6s
docker-based (debian-testing)	4m 15s
opam-based (ubuntu, 4.13.x)	7m 16s
docker-based (debian-unstable)	4m 11s
opam-based (ubuntu, 4.14.x, lower-bounds, no-doc)	8m 50s
docker-based (fedora)	4m 35s
opam-based (ubuntu, 4.14.x, deploy-doc)	7m 15s
docker-based (opensuse)	4m 38s
opam-based (ubuntu, 4.14.1, bytecode)	8m 38s
docker-based (oraclelinux)	4m 36s
opam-based (macos, 4.14.x)	19m 55s
docker-based (ubuntu)	4m 15s
opam-based (windows, 4.14.x, no-tests)	13m 4s
docker-based (ubuntu-lts)	4m 6s
opam-based (ubuntu, 5.0.x)	8m 58s
	2h 28m 51s

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