snappi:added fix for rx_l1_rate_gbps index error issue in traffic_generation.py file (sonic-net#16749)

Description of PR
Summary:
The metric 'Rx_L1_rate_Gbps' is picked from traffic item statistics. However, in 10.80, this is not working causing index error.

Switching it to Rx_L1_rate_bps in the statistics file.

Fixes # (issue)
sonic-net#16731

Approach
What is the motivation for this PR?
Resolving index error in the traffic item statistics. Instead of capturing Gbps rates, which no longer exists, switched to bps rates.

How did you do it?
Single line of code:

stats[metric_name+'_Rx_L1_Rate_bps'] = float(metric['Rx L1 Rate (bps)'])
How did you verify/test it?
Local clone.

co-authorized by: jianquanye@microsoft.com

Author: amitpawar12

tests/common/snappi_tests/traffic_generation.py

@@ -922,7 +922,7 @@ def tgen_curr_stats(traf_metrics, flow_metrics, data_flow_names):
         stats[metric_name+'_txrate_Gbps'] = tx_rate_gbps
         stats[metric_name+'_rxrate_fps'] = float(metric['Rx Frame Rate'])
         stats[metric_name+'_rxrate_Gbps'] = rx_rate_gbps
-        stats[metric_name+'_LI_rxrate_Gbps'] = float(metric['Rx L1 Rate (Gbps)'])
+        stats[metric_name+'_Rx_L1_Rate_bps'] = float(metric['Rx L1 Rate (bps)'])
 
     for metric in flow_metrics:
         if metric.name not in data_flow_names: