Remove redundant ArgumentAdderRector for nullable arguments

[GeniJaho]

Fixes #110

The 3 rules can be safely removed, as the methods previously did not expect a second parameter (framework change link).

The only class where the as parameter was put in the middle of two other parameters was Illuminate/Database/Capsule/Manager::table(), so I left that in the Laravel 6 set. The chances of extending it are small and, in that case, this rule would probably help.

Ideally, we'd also modify the original ArgumentAdderRector class to not add these default parameters in MethodCalls or StaticCalls, but that's another more complex problem.