Update parent to pom-scijava-base 19.0.0

This upgrades the maven-enforcer-plugin component stack to play
more nicely when updating components, particularly Jackson.

In particular, this update fixes the following error in the mega-melt:

    Failed to execute goal
    org.apache.maven.plugins:maven-enforcer-plugin:3.3.0:enforce
    (enforce-rules) on project mega-melt: Execution enforce-rules of
    goal org.apache.maven.plugins:maven-enforcer-plugin:3.3.0:enforce
    failed. NullPointerException

Author: ctrueden

pom.xml

@@ -5,7 +5,7 @@
 	<parent>
 		<groupId>org.scijava</groupId>
 		<artifactId>pom-scijava-base</artifactId>
-		<version>18.2.0</version>
+		<version>19.0.0</version>
 		<relativePath />
 	</parent>