fail2ban: fix `python3` references. (#109731)
fail2ban: fix `python3` references. (#109731)

See #108008.
Homebrew/homebrew-core,adam-moss/homebrew-core,filcab/homebrew-core,nandub/homebrew-core,filcab/homebrew-core,makigumo/homebrew-core,sjackman/homebrew-core,chrisfinazzo/homebrew-core,nandub/homebrew-core,adam-moss/homebrew-core,Homebrew/homebrew-core,lemzwerg/homebrew-core,stgraber/homebrew-core,chrisfinazzo/homebrew-core,lemzwerg/homebrew-core,stgraber/homebrew-core,makigumo/homebrew-core,sjackman/homebrew-core