[DOC] fix some comments

Signed-off-by: cui fliter <[email protected]>

lib/molinillo/resolution.rb

@@ -103,7 +103,7 @@ def reversed_requirement_tree_index
 
  # @return [Boolean] where the requirement of the state we're unwinding
  # to directly caused the conflict. Note: in this case, it is
- # impossible for the state we're unwinding to to be a parent of
+ # impossible for the state we're unwinding to be a parent of
  # any of the other conflicting requirements (or we would have
  # circularity)
  def unwinding_to_primary_requirement?