chore: use 5.2.0 for tests #27424

Job	Run time
Format	8m 48s
Coq 8.16.1	1m 24s
Coverage (5.2.x)	11m 22s
Build (macos-latest, 5.2.x)	13m 10s
Build (ubuntu-latest, 5.2.x)	9m 46s
MSVC 4.14.0 / windows_x86	10m 5s
Build (windows-latest, 5.2.x)	13m 5s
Documentation	37s
MSVC 4.14.0 / windows_x86_64	10m 0s
Nix (macos-latest)	6m 1s
Build (ocaml-variants.5.3.0+trunk, ubuntu-latest, true)	1m 56s
Nix (ubuntu-latest)	6m 17s
Build (5.2.x, macos-13, true)	5m 23s
Build (4.13.x, ubuntu-latest, true)	2m 6s
Create local opam switch (macos-latest, 5)	6m 39s
Build monorepo benchmark docker image	10m 15s
Build (4.08.x, ubuntu-latest, true)	2m 0s
Create local opam switch (macos-latest, 4.14)	6m 4s
Build (4.04.x, ubuntu-latest, true, true)	5m 0s
Create local opam switch (ubuntu-latest, 5)	4m 53s
Build (4.02.x, ubuntu-latest, true)	4m 24s
Create local opam switch (ubuntu-latest, 4.14)	5m 19s
	2h 24m 34s

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