MINOR: Exclude junit 3 transitive dependency from jfreechart (#9928)

This was causing IntelliJ to choose the Vintage runner when running `core` tests
which would then fail during the discovery phase.

Verified that `core` tests work in IntelliJ again after this change.

Reviewers: Chia-Ping Tsai <chia7712@gmail.com>

build.gradle

@@ -794,7 +794,9 @@ project(':core') {
     testCompile libs.apachedsJdbmPartition
     testCompile libs.junitJupiter
     testCompile libs.slf4jlog4j
-    testCompile libs.jfreechart
+    testCompile(libs.jfreechart) {
+      exclude group: 'junit', module: 'junit'
+    }
   }
 
   if (userEnableTestCoverage) {