Update slevomat/coding-standard to allow versions up to v8.20#25

Potherca wants to merge 2 commits intoMoxio:masterMoxio/php-codesniffer-sniffs:masterfrom

potherca-contrib:update/slevomat-coding-standard-to-8.20potherca-contrib/moxio-php-codesniffer-sniffs:update/slevomat-coding-standard-to-8.20Copy head branch name to clipboard