Since extending a class means including on the singleton class of the
class, this should now complain this:
``` ruby
module M
extend Gitlab::Utils::Override
override :f
def f
super.succ
end
end
class C
extend M
def self.f
0
end
end
```
It should complain because `C.f` wasn't calling `M#f`.
This should pass verification:
``` ruby
module M
extend Gitlab::Utils::Override
override :f
def f
super.succ
end
end
class B
def self.f
0
end
end
class C < B
extend M
end
```
Because `C.f` would now call `M#f`, and `M#f` does override something.
