Rectify javadoc for disabling management server port

[shollander]

According to the JavaDoc, setting the management.server.port property to 0 should disable the management server.

spring-boot/spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/web/server/ManagementServerProperties.java

Lines 67 to 72 in b5d19b7

	/**
	* Sets the port of the management server, use {@code null} if the
	* {@link ServerProperties#getPort() server port} should be used. To disable use 0.
	* @param port the port
	*/
	public void setPort(Integer port) {

However, according to the Reference Guide, setting the value to -1 is what is used to disable the http management server.

Based on empirical observation, the reference guide is correct. Setting the value of
management.server.port to 0 actually causes it to use a new random port for the management server, while setting the value to -1 will disable the management server.

[mbhave]

Closing in favor of #17068.