chore: update nstuning-api to v1.6.4 (#31)

Updates `nstuning-api` image tag to `v1.6.4` and bumps chart version to
`0.1.13`.

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: sondresjolyst

charts/nstuning-api/Chart.yaml

@@ -4,4 +4,4 @@ description: A Helm chart for Kubernetes
 
 type: application
 
-version: 0.1.12
+version: 0.1.13

charts/nstuning-api/values.yaml

@@ -3,7 +3,7 @@ replicaCount: 1
 image:
   repository: sondresjo/nstuning-api
   pullPolicy: IfNotPresent
-  tag: "v1.6.3"
+  tag: "v1.6.4"
 
 imagePullSecrets: []
 nameOverride: ""