[appmesh-gateway] nodeSelector indentation wrong

**Describe the bug**
I am trying to add nodeSelector, but it throws error from k8s. I think the indentation is wrong.

https://github.com/aws/eks-charts/blob/master/stable/appmesh-gateway/templates/deployment.yaml#L71

**Steps to reproduce**
add code
```
const gatewayChart = new HelmChart(this, 'AppMeshGatewayHelmChart', {
cluster,
namespace,
repository: 'https://aws.github.io/eks-charts',
chart: 'appmesh-gateway',
release: 'appmesh-gateway',
version: '0.1.5',
values: {
nodeSelector:{
nodeType: 'system',
},
},
});
```

throw exception:
```
unable to build kubernetes objects from release manifest: error validating "":
error validating data: ValidationError(Deployment.spec.template.spec):
unknown field "nodeType" in io.k8s.api.core.v1.PodSpec\n'
```

**Expected outcome**
should not throw error

**Environment**

* Chart name: appmesh-gateway
* Chart version: 0.1.5
* Kubernetes version: 1.19
* Using EKS (yes/no), if so version? yes

**Additional Context**:

Inspect stable/appmesh-gateway/templates/deployment.yaml around line 71 and render chart version 0.1.5 with the supplied nodeSelector values. Validate the generated Deployment against Kubernetes 1.19; done means the manifest accepts nodeSelector without placing nodeType directly in PodSpec.

Written by the indexing model from the issue text.