[#851] Update composer libs

[matthewhilton]

Closes #851

The issue seemed to be the old version of symfony was spamming a ton of debug output messages, and then eventually got stuck in what seemed an infinite loop.

Changes:

• Updated symfony/yaml from 3.4 -> 4.0.
  • 3.4 is the last 3.* version according to https://packagist.org/packages/symfony/yaml#v4.0.0
  • So I had to go to the next version, with is 4.0
  • 4.0 requires php 7.1 or above, so we should be good to make this a dataflows-wide change assuming tests pass seeing as we target php 7.4 and above

[keevan]

Hi Matt, it looks mostly good. I'm concerned about all the extra base composer file changes, and would like to keep it somewhat consistent.

Could you please check the changes here 851-update-dependencies...851-update-dependencies-extra-changes and see if you can cherry pick them into this PR?

All I need was update composer (composer self-update) and run the full install command in readme_moodle.txt.

[matthewhilton]

Good point - looks like my composer is on an older version as well. I just updated my composer to 2.6.6 and ran the composer update command which updated a few packages. Will wait and see if the CI passes now or if it still gets stuck

Edit: Looks like that didn't work either - so reverted back to previous, + cherry picked your commit, Kevin. Also had to re-add 4.2 as supported version so the CI runs for it.

[keevan]

Looks good, thanks Matt