docs(hertz)：fix typo in log example

Author: yusanwen-code

content/en/docs/hertz/tutorials/observability/log.md

@@ -18,7 +18,7 @@ func AccessLog() app.HandlerFunc {
 		start := time.Now()
 		c.Next(ctx)
 		end := time.Now()
-		latency := end.Sub(start).Microseconds
+		latency := end.Sub(start).Microseconds()
 		hlog.CtxTracef(ctx, "status=%d cost=%d method=%s full_path=%s client_ip=%s host=%s",
 			c.Response.StatusCode(), latency,
 			c.Request.Header.Method(), c.Request.URI().PathOriginal(), c.ClientIP(), c.Request.Host())

content/zh/docs/hertz/tutorials/observability/log.md

@@ -18,7 +18,7 @@ func AccessLog() app.HandlerFunc {
 		start := time.Now()
 		c.Next(ctx)
 		end := time.Now()
-		latency := end.Sub(start).Microseconds
+		latency := end.Sub(start).Microseconds()
 		hlog.CtxTracef(ctx, "status=%d cost=%d method=%s full_path=%s client_ip=%s host=%s",
 			c.Response.StatusCode(), latency,
 			c.Request.Header.Method(), c.Request.URI().PathOriginal(), c.ClientIP(), c.Request.Host())