Modify comment syntax error (#2572)

core/trace/agent.go

@@ -29,7 +29,7 @@ var (
 	tp     *sdktrace.TracerProvider
 )
 
-// StartAgent starts a opentelemetry agent.
+// StartAgent starts an opentelemetry agent.
 func StartAgent(c Config) {
 	lock.Lock()
 	defer lock.Unlock()

core/trace/config.go

@@ -3,7 +3,7 @@ package trace
 // TraceName represents the tracing name.
 const TraceName = "go-zero"
 
-// A Config is a opentelemetry config.
+// A Config is an opentelemetry config.
 type Config struct {
 	Name     string  `json:",optional"`
 	Endpoint string  `json:",optional"`