Update local variable name

Author: Blaisorblade

compiler/test/dotty/tools/vulpix/ParallelTesting.scala

@@ -1008,11 +1008,11 @@ trait ParallelTesting extends RunnerOrchestration { self =>
 
     /** Extract `Failure` set and render from `Test` */
     private[this] def reasonsForFailure(test: Test): String = {
-      val errors =
+      val failureReport =
         if (test.failureCount == 0) ""
-        else s"\n  - encountered ${test.failureCount} error(s)"
+        else s"\n  - encountered ${test.failureCount} test failures(s)"
 
-      errors + test.failureReasons.collect {
+      failureReport + test.failureReasons.collect {
         case test.TimeoutFailure(title) =>
           s"  - test '$title' timed out"
         case test.JavaCompilationFailure(msg) =>