Remove alias for `brew cask search`

In Homebrew (the upstream project), `brew cask search` was merged into `brew search` a few months ago [1].

On 2018-09-30, `brew cask search` will be disabled altogether [2].

Since the output of `brew cask search` used to be subject to change at any time and was never meant to be parsed, scripts should not rely on the `bcsr` alias. So I figure it may not hurt to remove the `bcsr` alias from Bash-it before that deadline.

[1]: https://github.com/Homebrew/brew/pull/4316

[2]: 990dd7de86

aliases/available/homebrew-cask.aliases.bash

@@ -7,7 +7,6 @@ alias bcin='brew cask install'
 alias bcrm='brew cask uninstall'
 alias bczp='brew cask zap'
 alias bccl='brew cask cleanup'
-alias bcsr='brew cask search'
 alias bcls='brew cask list'
 alias bcinf='brew cask info'
 alias bcdr='brew cask doctor'