Merge-ups not working with CMS 6 correctly

[emteknetnz]

Unable to work out a version of recipe-kitchen-sink to install, e.g.

` Problem 1

• silverstripe/recipe-kitchen-sink 5.x-dev requires silverstripe/recipe-content-blocks 3.x-dev -> satisfiable by silverstripe/recipe-content-blocks[3.x-dev].`

https://github.com/silverstripe/silverstripe-elemental/actions/runs/8130162250/job/22225084297#step:2:1132

Note: I'm going to resolve this merge-up manually so it'll probably be green by the time you read this

[emteknetnz]

Failed install isn't replicatable any more. I'm fairly sure it was failing at the bit where there was a mergeup from 5-6, REBUILD=1 so do an install of the module to merge into and install recipe-kitchen-sink * to see what version of admin gets installed

I extract this bit of code this bit of PHP code from action.yml where it was failing

  $COMPOSER_NAME = "dnadesign-silverstripe/elemental";
  $INTO_BRANCH = "6";
  $json = [
    "require" => [
      "$COMPOSER_NAME" => "$INTO_BRANCH.x-dev",
      "silverstripe/recipe-kitchen-sink" => "*"
    ],
    "prefer-stable" => false,
    "minimum-stability" => "dev"
  ];
  file_put_contents("composer.json", json_encode($json, JSON_UNESCAPED_SLASHES));
  shell_exec("composer update --no-install");
  $lock = json_decode(file_get_contents("composer.lock"), true);
  $version = array_values(array_filter(
    $lock["packages"],
    fn($p) => $p["name"] === "silverstripe/admin"
  ))[0]["version"];
  echo str_replace(".x-dev", "", $version);

However it now installs fine locally, whereas previously on the linked CI run it wouldn't install. Possibly issue was related to something not being updated on packagist at the time