Fix compute override for foreach tasks (#1357)

## Changes
Fix compute override for foreach tasks.

```
$ databricks bundle deploy --compute-id=xxx
```

## Tests
I added unit tests

bundle/config/mutator/override_compute.go

@@ -22,7 +22,12 @@ func (m *overrideCompute) Name() string {
 
 func overrideJobCompute(j *resources.Job, compute string) {
 	for i := range j.Tasks {
-		task := &j.Tasks[i]
+		var task = &j.Tasks[i]
+
+		if task.ForEachTask != nil {
+			task = &task.ForEachTask.Task
+		}
+
 		if task.NewCluster != nil || task.ExistingClusterId != "" || task.ComputeKey != "" || task.JobClusterKey != "" {
 			task.NewCluster = nil
 			task.JobClusterKey = ""

bundle/config/mutator/override_compute_test.go

@@ -115,6 +115,31 @@ func TestOverridePipelineTask(t *testing.T) {
 	assert.Empty(t, b.Config.Resources.Jobs["job1"].Tasks[0].ExistingClusterId)
 }
 
+func TestOverrideForEachTask(t *testing.T) {
+	t.Setenv("DATABRICKS_CLUSTER_ID", "newClusterId")
+	b := &bundle.Bundle{
+		Config: config.Root{
+			Resources: config.Resources{
+				Jobs: map[string]*resources.Job{
+					"job1": {JobSettings: &jobs.JobSettings{
+						Name: "job1",
+						Tasks: []jobs.Task{
+							{
+								ForEachTask: &jobs.ForEachTask{},
+							},
+						},
+					}},
+				},
+			},
+		},
+	}
+
+	m := mutator.OverrideCompute()
+	diags := bundle.Apply(context.Background(), b, m)
+	require.NoError(t, diags.Error())
+	assert.Empty(t, b.Config.Resources.Jobs["job1"].Tasks[0].ForEachTask.Task)
+}
+
 func TestOverrideProduction(t *testing.T) {
 	b := &bundle.Bundle{
 		Config: config.Root{