collab: Remove Stripe code (#36275)

This PR removes the code for integrating with Stripe from Collab.

All of these concerns are now handled by Cloud.

Release Notes:

- N/A

crates/collab/k8s/collab.template.yml

@@ -219,12 +219,6 @@ spec:
                 secretKeyRef:
                   name: slack
                   key: panics_webhook
-            - name: STRIPE_API_KEY
-              valueFrom:
-                secretKeyRef:
-                  name: stripe
-                  key: api_key
-                  optional: true
             - name: COMPLETE_WITH_LANGUAGE_MODEL_RATE_LIMIT_PER_HOUR
               value: "1000"
             - name: SUPERMAVEN_ADMIN_API_KEY