Don't use deprecated PGPPublicKeyRingCollection constructor

The PGPPublicKeyRingCollection constructor was deprecated in
Bouncycastle v1.51.

Use BcPGPPublicKeyRingCollection instead.

Change-Id: I5bc4fb4927ba37ecbf7d3763809acc2f53d7fd4e
(cherry picked from commit d26e43f22f2336efd18213ac88c285f8b95827cd)
Fix incorrect formatting in json documentation

Change-Id: Idaf47978ddd09c9f7a5708efb7d70afcfb8899f8