Polishing.

Original pull request #1895

spring-data-r2dbc/src/main/java/org/springframework/data/r2dbc/mapping/OutboundRow.java

@@ -227,6 +227,6 @@ public class OutboundRow implements Map<SqlIdentifier, Parameter>, Cloneable {
 	}
 
 	private static Object convertKeyIfNecessary(Object key) {
-		return key instanceof String string ? SqlIdentifier.unquoted(string) : key;
+		return key instanceof String keyString ? SqlIdentifier.unquoted(keyString) : key;
 	}
 }