Bump kotlin version to latest 1.4-M2

These artifacts are now available from the SciJava Public maven repo,
removing any obstacles to using the latest kotlin in our projects.

Closes scijava/pom-scijava#124

Author: hinerm

pom.xml

@@ -274,7 +274,7 @@
 
 		<!-- Plugin dependencies -->
 		<extra-enforcer-rules.version>1.2</extra-enforcer-rules.version>
-		<kotlin.version>1.3.72</kotlin.version>
+		<kotlin.version>1.4-M2</kotlin.version>
 		<revapi-java.version>0.20.2</revapi-java.version>
 		<scijava-coding-style.version>2.0.0</scijava-coding-style.version>
 		<velocity.version>1.7</velocity.version>