Stop generating MD5, SHA1 and SHA512 with Ant

Currently there is still manual generation of MD5, SHA1 and SHA512 checksum via Ant in https://github.com/apache/jackrabbit-filevault/blob/3c9f668fc608c815db154b2569bf16c71f668428/pom.xml#L325-L340 and https://github.com/apache/jackrabbit-filevault-package-maven-plugin/blob/c0433155e825130d1c9a435f5fb837af8e9c46d4/pom.xml#L744-L759.

MD5 and SHA1 should no longer be provided according to https://infra.apache.org/release-distribution.html#sigs-and-sums and SHA512 is automatically created through the ASF parent pom (https://maven.apache.org/pom/asf/#the-apache-release-profile).

In https://jackrabbit.apache.org/jcr/downloads.html#vlt we only link the SHA512 anyways.

Note: This is only about ASF dist not about the checksums used in Maven repositories which are transparently created by Maven Resolver.