Bump copyright years.
Bump copyright years.

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