Remove reference to addresses + keys, which is now in its own chapter

Signed-off-by: Jesse Pinho <[email protected]>

docs/protocol/src/protocol.md

@@ -3,8 +3,6 @@
 This chapter describes the cryptographic design of the Penumbra protocol,
 described in more detail in the following sections:
 
-- The [Addresses and Keys](./protocol/addresses_keys.md) section describes the Penumbra key hierarchy and diversified addresses.
-
 - The [Notes](./protocol/notes/note_ciphertexts.md) section describes Penumbra's private notes and their contents.
 
 - The [Transaction Cryptography](./protocol/transaction_crypto.md) section describes the symmetric keys used at the level of an individual transaction.