Pre Kubernetes v1.20, exec livenessprobes `timeoutSeconds` wasn't functional, and defaults to 1 second. The livenessprobe for the scheduler, however, takes longer than 1 second to finish so the scheduler will have consistent livenessprobe failures when running on v1.20.

> Before Kubernetes 1.20, the field timeoutSeconds was not respected for exec probes: probes continued running indefinitely, even past their configured deadline, until a result was returned.

```
...
  Warning  Unhealthy  23s    kubelet            Liveness probe failed:
```

https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/#configure-probes

**Kubernetes version**: v1.20.2

**What happened**:

Livenessprobe failures keeps restarting the scheduler due to timing out.

**What you expected to happen**:

Livenessprobe succeeds.

**How to reproduce it**:

Deploy the helm chart on v1.20+ with the default livenessprobe `timeoutSeconds` of 1 and watch the scheduler livenessprobe fail.

chart/tests/test_scheduler.py
"""
        Test scheduler kind is StatefulSet only when using LocalExecutor &
        worker persistence is enabled.
        """
        docs = render_chart(
            values={
                "executor": executor,
                "workers": {"persistence": {"enabled": persistence}},
            },
            show_only=["templates/scheduler/scheduler-deployment.yaml"],
        )
        assert kind == jmespath.search("kind", docs[0])
    def test_should_add_extra_containers(self):
        docs = render_chart(
            values={
                "executor": "CeleryExecutor",
                "scheduler": {
                    "extraContainers": [
                        {
                            "name": "test-container",
                            "image": "test-registry/test-repo:test-tag",
                            "imagePullPolicy": "Always",
                        }
                    ],
                },
            },
            show_only=["templates/scheduler/scheduler-deployment.yaml"],
        )
        assert "test-container" == jmespath.search("spec.template.spec.containers[-1].name", docs[0])
    def test_should_add_extra_volume_and_extra_volume_mount(self):