Replacing SCM tags (required by sonatype)

Removed snapshot for release 1.5.3

Update to Java 21 (#188)

* Setting maven.compiler.release to 21

* Updating nexus staging maven plugin

* Updated source/Javadoc plugin

[maven-release-plugin] copy for tag jsonassert-1.5.1

[maven-release-plugin] copy for tag jsonassert-1.5.0

[maven-release-plugin] copy for tag jsonassert-1.4.0

[maven-release-plugin] copy for tag jsonassert-1.3.0

[maven-release-plugin] copy for tag jsonassert-1.2.3

[maven-release-plugin] copy for tag jsonassert-1.2.2

[maven-release-plugin] copy for tag jsonassert-1.2.1