Add comment to pom in sample explaining provided deps

spring-boot-samples/spring-boot-sample-war/pom.xml

 <?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
 	<modelVersion>4.0.0</modelVersion>
 	<parent>
 		<!-- Your own application should inherit from spring-boot-starter-parent -->
@@ -27,6 +28,7 @@
 			<artifactId>spring-boot-starter</artifactId>
 		</dependency>
 		<dependency>
+			<!-- To build an executable war use one of the profiles below -->
 			<groupId>javax.servlet</groupId>
 			<artifactId>javax.servlet-api</artifactId>
 			<scope>provided</scope>