Upgrade to JaCoCo 0.8.6 to fix failing JDK 15 build.

Author: michael-simons

pom.xml

@@ -92,7 +92,7 @@
 		<checkstyle.version>8.29</checkstyle.version>
 		<project.build.docs>${project.build.directory}/docs</project.build.docs>
 		<flatten-maven-plugin.version>1.1.0</flatten-maven-plugin.version>
-		<jacoco-maven-plugin.version>0.8.5</jacoco-maven-plugin.version>
+		<jacoco-maven-plugin.version>0.8.6</jacoco-maven-plugin.version>
 		<java.version>1.8</java.version>
 		<maven.version>3.6.1</maven.version>
 		<maven-checkstyle-plugin.version>3.1.0</maven-checkstyle-plugin.version>