zetacored : remove msg type url for events emitted from begin or end block

[kingpinXD]

The following events are emitted from begin block of emissions module.

message EventObserverEmissions {
  string msg_type_url = 1;
  repeated ObserverEmission emissions = 2;
}
message EventBlockEmissions {
  string msg_type_url = 1;
  string bond_factor = 2;
  string reserves_factor = 3;
  string duration_factor = 4;
  string validator_rewards_for_block = 5;
  string observer_rewards_for_block = 6;
  string tss_rewards_for_block = 7;
}

They currently have a hard-coded value for the field msg_type_url , which should be removed as there is no message associated with these events

[kingpinXD]

Note : We should verify that this field is not currently being used before removing it completely