Fix a warning preventing pod spec validation. (#2989)
Fix a warning preventing pod spec validation. (#2989)

* Fix a warning preventing pod spec validation.

* Add comment, thanks @adlai.

tomizimobile/AsyncDisplayKit,maicki/AsyncDisplayKit,maicki/AsyncDisplayKit,maicki/AsyncDisplayKit,lappp9/AsyncDisplayKit,rmls/AsyncDisplayKit,tomizimobile/AsyncDisplayKit,lappp9/AsyncDisplayKit,rmls/AsyncDisplayKit,flovouin/AsyncDisplayKit,rmls/AsyncDisplayKit,flovouin/AsyncDisplayKit,maicki/AsyncDisplayKit,maicki/AsyncDisplayKit,tomizimobile/AsyncDisplayKit,rmls/AsyncDisplayKit,tomizimobile/AsyncDisplayKit,lappp9/AsyncDisplayKit,tomizimobile/AsyncDisplayKit,flovouin/AsyncDisplayKit,lappp9/AsyncDisplayKit,rmls/AsyncDisplayKit,flovouin/AsyncDisplayKit,flovouin/AsyncDisplayKit