Fix joining single line Ruby methods without arguments

[gsamokovarov]

Joining single-line Ruby method without arguments into an endless method definition was not working as the regexp pattern expected the def always to accept parenthesized arguments.

Example:

def foo()
  bar
end

Would be joined to:

def foo() = bar

However, the following, which is the idiomatic way to write Ruby methods without arguments, would not:

def foo
  bar
end

[AndrewRadev]

I think at the time when I was experimenting, I tried def foo= bar, which doesn't work, since foo= can be a method name itself. I don't remember if ruby itself didn't work without the brackets back then or if I missed checking def foo = bar, but either way, this seems to work fine 👍. Thanks for putting in the work, especially the tests.