brew irb --help replaced with --examples
brew irb --help replaced with --examples

The --help flag is intercepted by brew.rb and prints the global usage
string. `irb` is never called when `brew irb --help` is executed.

Closes Homebrew/homebrew#35466.

Signed-off-by: Jack Nagel <43386ce32af96f5c56f2a88e458cb94cebee3751@gmail.com>

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