compserのアップグレード

Warning from https://repo.packagist.org: You are using an outdated version of Composer. Composer 2.0 is now available and you should upgrade. See https://getcomposer.org/2

# composer selfupdate
Updating to version 2.0.10 (stable channel).
   Downloading (100%)         
Use composer self-update --rollback to return to version 1.8.0