cachetool not compatible with php < 7.1 anymore

[shuryoka]

The task "cachetool:clear:opcache" from "deployer/recipies" always downloads the most up to date version. As of today this is version 4.0.0. But this is not compatible with PHP versions smaller than 7.1 anymore (https://github.com/gordalina/cachetool/issues/73).

The deployer recipe is already updated and can be used with version 6.1.2 (https://github.com/deployphp/recipes/releases/tag/6.1.2). But currently the composer.json here does not load the 6.1.x versions.