springboot Spring Boot's antlib references a properties file that is no longer packaged in its jar

https://github.com/spring-projects/spring-boot/blob/4910b518779ed6606b96bb77829dbf2839668a7e/spring-boot-project/spring-boot-tools/spring-boot-antlib/src/main/resources/org/springframework/boot/ant/antlib.xml#L37-L46

The file isn't packaged in any 2.x version. It is there in 1.5.x. I'm not yet sure if its absence is breaking something and no one has noticed or if it's not needed and we can remove the reference to it.

Comment From: wilkinsona

As far as I can tell, it does not serve any purpose. The version property doesn't appear to be used anywhere and its value will be the same as the spring-boot.version property that's used elsewhere. I think we can remove the loading of the properties. Doing so will stop the following from being output when using the antlib:

[loadproperties] Unable to find resource META-INF/maven/org.springframework.boot/spring-boot-antlib/pom.properties