Update index.md

Author: bill-wilkin

src/connections/destinations/catalog/actions-google-analytics-4/index.md

@@ -211,6 +211,7 @@ Google reserves certain event names, parameters, and user properties. Google sil
 - fields or events with reserved names
 - fields with a number as the key
 - fields or events with a dash (-) character in the name
+- property name with capital letters
 
 ### Verifying Event Meet GA4's Measurement Protocol API
 **Why are the events returning an error _Param [PARAM] has unsupported value._?**