update composer plugin api version

[mauriau]

Composer just merged the branch 2.0 into master.
composer/composer@87757de

So we got this issue :
- hirak/prestissimo 0.3.10 requires composer-plugin-api ^1.0.0 -> found composer-plugin-api[2.0.0] but it does not match your constraint.

[baukevdw]

For more information see: composer/composer#8726

[Seldaek]

For prestissimo, as composer 2 comes with parallel downloads built-in, it probably makes more sense to not support v2, or to support it but to disable prestissimo completely if composer version is 2.