nixos/meilisearch: allow access to proc for memory limit (#442565)

        LockPersonality = true;

        MemoryDenyWriteExecute = true;

        ProcSubset = "pid";

        # Meilisearch needs to determine cgroup memory limits to set its own memory limits.

        # This means this can't be set to "pid"

        ProcSubset = "all";

        ProtectProc = "invisible";

        NoNewPrivileges = true;