Recommend overriding licences and developers when using starter parent

Publishing to Maven Central requires spring-boot-starter-parent to
declare its license and developers. When a user then uses
spring-boot-starter-parent as their project's parent, these values
are inherited and this is almost certainly unwanted.

This commit updates the documentation to recommend and demonstrate
overriding the license and developers that are inherited from the
starter parent.

Closes gh-18532

Author: wilkinsona

spring-boot-project/spring-boot-docs/src/main/asciidoc/getting-started.adoc

@@ -130,6 +130,14 @@ The following listing shows a typical `pom.xml` file:
 			<version>{spring-boot-version}</version>
 		</parent>
 
+		<!-- Override inherited license and developers -->
+		<licenses>
+ 			<license />
+ 		</licenses>
+ 		<developers>
+ 			<developer />
+ 		</developers>
+
 		<!-- Add typical dependencies for a web application -->
 		<dependencies>
 			<dependency>
@@ -462,6 +470,13 @@ Open your favorite text editor and add the following:
 			<version>{spring-boot-version}</version>
 		</parent>
 
+		<licenses>
+ 			<license />
+ 		</licenses>
+ 		<developers>
+ 			<developer />
+ 		</developers>
+
 		<!-- Additional lines to be added here... -->
 
 ifeval::["{spring-boot-artifactory-repo}" != "release"]