Delete PopUpMenu.podspec,json

[kmmtampes]

Deprecate PopUpMenu pod

[kylef]

Hi @kmmtampes, deprecation can be done by adding a "deprecated" flag to the podspec.

{
  "deprecated": true
}

Deleting the pod spec isn't quite deprecating it and will instead cause problems for anyone who depends on this.

[keith]

Submit a new PR deprecating if you'd like.