Pass Gandi URL as an input, not a secret

Signed-off-by: Benoit Donneaux <benoit@leastauthority.com>

Author: btlogy

.github/workflows/_terraform.yml

@@ -50,7 +50,7 @@ jobs:
         working-directory: ${{ inputs.tf_dir }}
     env:
       TF_VAR_gandi_token: ${{ secrets.gandi_token }}
-      TF_VAR_gandi_url: ${{ secrets.gandi_url }}
+      TF_VAR_gandi_url: ${{ inputs.gandi_url }}
       TF_VAR_hcloud_token: ${{ secrets.hcloud_token }}
     permissions:
       pull-requests: write