Fix chplcheck bug with IncorrectIndentation and attributes

[jabraham17]

Fixes an issue with the IncorrectIndentation lint rule where a module level attribute was treated as a child of the module

For example:

@myAttribute() // Warning: IncorrectIndentation
module foo {
  ...
}

This is fixed by skipping the AttributeGroup, if it exists

Tested locally

[Reviewed by @DanilaFe]