Increase psr/log requirement

[fritzmg]

This PR increases the psr/log requirement for easier installation in Contao. Currently you can only install this extension with

composer require netzmacht/contao-i18n --no-update && composer update

or

composer require netzmacht/contao-i18n -W

or by adding in the Contao Manager and then "Update all packages" (rather than "Apply").

With this change the extension can be installed regularly (i.e. without having to downgrade psr/log).

[dmolineus]

Thanks @fritzmg