Remove Health from Status Report message (#32)

OpenTelemetry is now working on defining how the health status should
be reported via metrics: open-telemetry/oteps#185

I am removing it from here so that if the metric is added we can use that.
In the unlikely even the metric is not added we can think whether we really
need it as a field in OpAMP.

README.md

@@ -472,7 +472,6 @@ message StatusReport {
     EffectiveConfig effective_config = 2;
     RemoteConfigStatus remote_config_status = 3;
     bytes server_provided_all_addons_hash = 4;
-    HealthStatus health_status = 5;
 }
 ```
 
@@ -517,27 +516,6 @@ The server SHOULD compare this hash to the aggregate hash of all addons that it
 has for this Agent and if the hashes are different the server SHOULD send an
 AddonsAvailable message to the agent.
 
-<h4 id="health_status">health_status</h4>
-
-
-Indicates whether the agent is healthy or not. The value is one of the enum:
-
-
-```protobuf
-enum HealthStatus {
-    // The health status is unchanged since last reported.
-    HealthUnset = 0;
-    // The agent is healthy.
-    Healthy = 1;
-    // The agent is unhealthy.
-    Unhealthy = 2;
-}
-```
-
-
-More granular health information is expected to be reported by the Agent as
-described in [Own Telemetry Reporting](#own-telemetry-reporting).
-
 <h3 id="agentdescription-message">AgentDescription Message</h3>