Revert temporary Calico workaround once rke2-calico chart bug is fixed

The rke2-calico chart currently renders invalid fields in the Installation CR:

- .spec.natOutgoing 
- .spec.backend

These fields are not part of the Tigera operator schema and cause validation errors.

A temporary workaround is added in Draft: Enable drift correction for calico HR (!5756) · Merge requests · Sylva-projects / sylva-core · GitLab by setting these values to null:

installation:
  natOutgoing: null
  backend: null

This issue is to revert the workaround once the upstream chart is corrected.

Details:

Due to the chart template logic, natOutgoing and backend remain under .Values.installation and are incorrectly rendered at the root of .spec.

Upstream issue: rke2-calico: natOutgoing and backend fields incorrectly rendered under .spec in Installation CR · Issue #9301 · rancher/rke2

Affected since: v3.29.201