Upgrade to JaCoCo 0.8.7

This version has "experimental" support for Java 17. See https://github.com/jacoco/jacoco/issues/1148

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1893782 13f79535-47bb-0310-9956-ffa450edef68

build.gradle

@@ -306,7 +306,7 @@ subprojects {
     }
 
     jacoco {
-        toolVersion = '0.8.6'
+        toolVersion = '0.8.7'
     }
 
     jacocoTestReport {