change telemetry name for dd-trace-api (#5264)

This is as per the landed change in dd-go.

Author: bengl

packages/datadog-plugin-dd-trace-api/src/index.js

@@ -28,7 +28,7 @@ module.exports = class DdTraceApiPlugin extends Plugin {
     })
 
     const handleEvent = (name) => {
-      const counter = apiMetrics.count('dd_trace_api.called', [
+      const counter = apiMetrics.count('public_api.called', [
         `name:${name.replaceAll(':', '.')}`,
         'api_version:v1',
         injectionEnabledTag