stream: fix missing pointer in Send call

[mortelli]

This PR is analogous to #1765; only it is applied to the stream protocol rather than the retrieve protocol.

• the bug: there's a struct passed to a peer.Send call, which should be passed as a pointer instead of a plain struct
  • the call is made inside of the updateSyncSubscriptions function
  • the struct in question is the StreamInfoReq message
• the bug was discovered while trying to implement accounting in the stream protocol
  • a reflect call with the purpose of adding price to the message will panic if the struct is passed as a value
  • accounting on top of the stream protocol might end up not being merged, but we should merge this fix anyways