Update composer/composer to ^1.9.1

Composer 1.9 is only required for Drupal core development. If you are using a drupal-composer/drupal-project based site, then older versions of Composer still work.

Also we require composer 1.9 to be installed as your global tool when working with the git clone of drupal as a core developer, *however* when we require composer/composer as a dev dependency that is so that we can use it for testing the composer plugins that are written into core, and as such it acts like a library and not a tool in that case.

It probably wouldnt hurt to bump it to 1.9, but its not totally necessary.

Here's attempt

the one for 8.9.x

So in order to generate this patch you need to:
1. Update composer.json
2. Run composer update composer/composer
3. Run composer update --lock (to remove the composer bin entry from the lock file)

That last step is not fun.

This patch is only a reroll of the last patch...

(to remove the composer bin entry from the lock file)

Im very much unsure why this is happening, or why it keeps coming back.