what is that error ?
composer.json you have to remove the
"post-autload-dump" line because it does nothing with composer >2.0 (which you are using)
It is still necesary when you use composer 1.x, make sure you upgrade composer everywhere before deleting it
The error message tells you exactly what the problem is and how to fix it.
It’s not required for any composer version with plugin-installer 1.3.