Update requirements for 3.x

The test failures here look like this:

Testing Drupal\Tests\automatic_updates\Build\CoreUpdateTest
FFFFF                                                               5 / 5 (100%)

Time: 01:57.671, Memory: 14.00 MB

There were 5 failures:

1) Drupal\Tests\automatic_updates\Build\CoreUpdateTest::testApi
COMMAND: COMPOSER_MIRROR_PATH_REPOS=1 composer require --update-with-all-dependencies "drupal/automatic_updates:@dev"
OUTPUT:
ERROR: ./composer.json has been updated
Running composer update drupal/automatic_updates --with-all-dependencies
Loading composer repositories with package information
Updating dependencies
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Root composer.json requires drupal/automatic_updates @dev -> satisfiable by drupal/automatic_updates[dev-merge-request-699].
    - drupal/automatic_updates dev-merge-request-699 requires drupal/core ^10 -> found drupal/core[9.8.0] but it does not match the constraint.

… which is what I encountered a few weeks ago and opened #3337049: Assert no errors after creating the test project in ModuleUpdateTest for.

Pushed a commit to see if my new theory (after #4) is correct: if it is correct, we should get past the composer errors, and instead we should start seeing failures when modules are being installed … 🤓

Looks like my theory in #5 worked — that means I disproved my theory in #4 🤓 — this does not need to be postponed on #3337049: Assert no errors after creating the test project in ModuleUpdateTest anymore!

Hopefully that'll be green now! 🤞

Left to do: address the @todo in \Drupal\Tests\automatic_updates\Functional\AvailableUpdatesReportTest::assertVersionLink(). Assigning to @phenaproxima since he added that — it's not entirely clear to me what should happen there — I think the entire assertion method should be dropped and all calls to it, but that'd be equivalent to losing test coverage…

Assigning to @tedbow for review.

I decided to keep assertVersionLink(), but changed it assertVersionIsListed() to more accurately reflect what it does. The Download link is no longer visible, which is a core change that core should be testing.