Update 1.3.3 Spec to remove SSL Pinning macro

Update the 1.3.3 podspec to correctly reflect the 1.3.3 podspec listed on the official tag: https://github.com/AFNetworking/AFNetworking/blob/1.3.3/AFNetworking.podspec
Merge pull request #6103 from SRandazzo/patch-1

Update 1.3.3 Spec to remove SSL Pinning macro