build(maven): bump pom.xml to 4.0-SNAPSHOT (#2286)

Author: galtm

pom.xml

@@ -5,7 +5,7 @@
   <modelVersion>4.0.0</modelVersion>
   <groupId>io.xspec</groupId>
   <artifactId>xspec</artifactId>
-  <version>3.4.3</version>
+  <version>4.0-SNAPSHOT</version>
 
   <name>XSpec implementation</name>
   <description>A unit test framework for XSLT, XQuery and Schematron</description>