updated env sample

Author: AjitPadhi-Microsoft

src/backend/.env.sample

@@ -38,5 +38,6 @@ BING_CONNECTION_NAME=
 AZURE_BASIC_LOGGING_LEVEL=INFO
 # Azure package logging (default: WARNING level to suppress INFO)
 AZURE_PACKAGE_LOGGING_LEVEL=WARNING
-# Azure logging packages (comma-separated list, no logging config if blank)
+# Comma-separated list of specific logger names to configure (default: empty - no custom loggers)
+# Example: AZURE_LOGGING_PACKAGES=azure.identity.aio._internal,azure.monitor.opentelemetry.exporter.export._base
 AZURE_LOGGING_PACKAGES=