overrides: raise source-controller max helm index size

For truecharts:
https://github.com/fluxcd/flux2/issues/4635

overrides/source-controller-patch.yaml

+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+patches:
+  - patch: |
+      - op: add
+        path: /spec/template/spec/containers/0/args/-
+        value: --helm-index-max-size=80000000
+    target:
+      kind: Deployment
+      name: "source-controller"