docs: use https:// instead of git://

INSTALL.md

@@ -21,7 +21,7 @@ How to install
 
 Simply clone this repository and source the script:
 
-        git clone git://github.com/zsh-users/zsh-syntax-highlighting.git
+        git clone https://github.com/zsh-users/zsh-syntax-highlighting.git
         echo "source ${(q-)PWD}/zsh-syntax-highlighting/zsh-syntax-highlighting.zsh" >> ~/.zshrc
         source ~/.zshrc
 
@@ -42,7 +42,7 @@ To install zsh-syntax-highlighting under oh-my-zsh:
 
 1. Clone this repository in oh-my-zsh's plugins directory:
 
-        git clone git://github.com/zsh-users/zsh-syntax-highlighting.git ~/.oh-my-zsh/custom/plugins/zsh-syntax-highlighting
+        git clone https://github.com/zsh-users/zsh-syntax-highlighting.git ~/.oh-my-zsh/custom/plugins/zsh-syntax-highlighting
 
 2. Activate the plugin in `~/.zshrc`: