Mark OriginTrackedPropertiesLoader#isNewDocument private

See gh-24268

Author: JimStockwell

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/env/OriginTrackedPropertiesLoader.java

@@ -160,7 +160,7 @@ private OriginTrackedValue loadValue(StringBuilder buffer, CharacterReader reade
 		return OriginTrackedValue.of(buffer.toString(), origin);
 	}
 
-	boolean isNewDocument(CharacterReader reader) throws IOException {
+	private boolean isNewDocument(CharacterReader reader) throws IOException {
 		if (reader.isLastLineComment()) {
 			return false;
 		}