docs: fix recall formula label in SQL metrics documentation

The formula on line 20 was incorrectly labeled as 'Precision' when it actually
represents the Recall formula (denominator uses 'Total number of rows in reference').

Precision uses rows in response as denominator (line 16).
Recall uses rows in reference as denominator (line 20).

Fixes #2404

Author: tysoncung

docs/concepts/metrics/available_metrics/sql.md

@@ -17,7 +17,7 @@ $$
 $$
 
 $$
-\text{Precision } = {|\text{Number of matching rows in response and reference}| \over |\text{Total number of rows in reference}|}
+\text{Recall } = {|\text{Number of matching rows in response and reference}| \over |\text{Total number of rows in reference}|}
 $$
 
 By default, the mode is set to `row`, and metric is F1 score which is the harmonic mean of precision and recall.