Update appveyor to PHP 7.3
Update appveyor to PHP 7.3

milleruk/composer,floverdevel/composer,localheinz/composer,nicolas-grekas/composer,stefangr/composer,composer/composer,alcohol/composer,pierredup/composer,naderman/composer,fabpot/composer,andrerom/composer,stof/composer,johnstevenson/composer,staabm/composer