driver: Improve comment about ^r pattern match bug
driver: Improve comment about ^r pattern match bug

The bug is not specific to 5.3.1.

joshuarubin/dotfiles,P71/zsh-syntax-highlighting,phy1729/zsh-syntax-highlighting,P71/zsh-syntax-highlighting,danielshahaf/zsh-syntax-highlighting,x-way/zsh-syntax-highlighting,stuha/wbr-zsh,zsh-users/zsh-syntax-highlighting,danielshahaf/zsh-syntax-highlighting,x-way/zsh-syntax-highlighting,joshuarubin/dotfiles,phy1729/zsh-syntax-highlighting,joshuarubin/dotfiles,zsh-users/zsh-syntax-highlighting,joshuarubin/dotfiles