[PR][php-langspec][#157][master] - Removed Throwable Interface Method Modifiers

You can view the Pull Request on github: https://github.com/php/php-langspec/pull/157 Pull Request Description: > All methods declared in an interface must be implicitly or explicitly public, and they must not be declared abstract. This quote is directly from the specification itself, however, the Throwable interface uses the abstract modifier and a public access modifier (unlike all other interfaces in the same document). I removed both modifiers from the methods in the Throwable interface example to ensure consistency. And apparently the required function keyword was missing too.