Update homebrew install command to fix the error

[1matin]

The brew cask command is now deprecated and will cause an error as below:

% brew cask install telegram
Error: `brew cask` is no longer a `brew` command. Use `brew <command> --cask` instead.

I changed the command to the new form that homebrew accepts, which is brew ... --cask.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
1 out of 2 committers have signed the CLA.

✅ 1matin
❌ overtake
_{You have signed the CLA already but the status is still pending? Let us recheck it.}