remove all UnnecessaryPublicModifier linter issues

flag = none
refs: DE-643

Change-Id: I251321e6558ad1b7a0a36d1053a7b02f393bd233
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/264178
Reviewed-by: Aaron Ogata <aogata@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
QA-Review: Andrea Cirulli <andrea.cirulli@instructure.com>
Product-Review: Andrea Cirulli <andrea.cirulli@instructure.com>

build/new-jenkins/library/test/integration/groovy/BaseTest.groovy

@@ -25,6 +25,7 @@ import com.lesfurets.jenkins.unit.*
 class BaseTest extends BasePipelineTest {
   // Implement a rule to intercept test failures and print the callStack
   @Rule
+  /* groovylint-disable-next-line UnnecessaryPublicModifier */
   public final TestRule testRule = new TestWatcher() {
     @Override
     protected void failed(Throwable e, Description description) {