[SPARK-36048][TEST][CORE] Fix HealthTrackerSuite.allExecutorAndHostIds

### What changes were proposed in this pull request?

Fix the executor ids that are declared at `allExecutorAndHostIds`.

### Why are the changes needed?

Currently, `HealthTrackerSuite.allExecutorAndHostIds` is mistakenly declared, which leads to the executor exclusion isn't correctly tested.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Pass existing tests in `HealthTrackerSuite`.

Closes apache#33262 from Ngone51/fix-healthtrackersuite.

Authored-by: yi.wu <yi.wu@databricks.com>
Signed-off-by: yi.wu <yi.wu@databricks.com>

core/src/test/scala/org/apache/spark/scheduler/HealthTrackerSuite.scala

@@ -62,11 +62,11 @@ class HealthTrackerSuite extends SparkFunSuite with BeforeAndAfterEach with Mock
   // All executors and hosts used in tests should be in this set, so that [[assertEquivalentToSet]]
   // works.  Its OK if its got extraneous entries
   val allExecutorAndHostIds = {
-    (('A' to 'Z')++ (1 to 100).map(_.toString))
-      .flatMap{ suffix =>
+    ('A' to 'Z')
+      .flatMap { suffix =>
         Seq(s"host$suffix", s"host-$suffix")
       }
-  }.toSet
+  }.toSet ++ (1 to 100).map(_.toString)
 
   /**
    * Its easier to write our tests as if we could directly look at the sets of nodes & executors in