Fix checkstyle violation

Author: snicoll

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/env/EnvironmentEndpoint.java

@@ -167,7 +167,7 @@ private static class PropertySourcesPlaceholdersSanitizingResolver
 
 		private final Sanitizer sanitizer;
 
-		public PropertySourcesPlaceholdersSanitizingResolver(
+		PropertySourcesPlaceholdersSanitizingResolver(
 				Iterable<PropertySource<?>> sources, Sanitizer sanitizer) {
 			super(sources, new PropertyPlaceholderHelper(
 					SystemPropertyUtils.PLACEHOLDER_PREFIX,