update OCaml to 5.1.1-rc1 / js_of_ocaml to 5.5.1 #3793

Job	Run time
nix-fmt-check	1m 33s
Native packages (Linux, OCaml 4_14)	11m 25s
Native packages (macOS, OCaml 4_14)	27m 5s
arm64 packages (OCaml 4_14)	1m 1s
Native packages (Linux, OCaml 5_0)	9m 46s
Native packages (macOS, OCaml 5_0)	34m 26s
Native packages (Linux, OCaml 5_1)	1h 56m 11s
musl packages (OCaml 4_14)	52s
Native packages (macOS, OCaml 5_1)	6h 4m 58s
arm64 packages (OCaml 5_0)	59s
Native (Top-level) packages (ubuntu-latest)	1m 13s
musl packages (OCaml 5_0)	52s
Native (Top-level) packages (macos-13)	2m 13s
arm64 packages (OCaml 5_1)	27m 58s
musl packages (OCaml 5_1)	15m 40s
	10h 16m 12s

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