acc: add cleanup trap to postgres acceptance tests (#4489)

## Summary
Add cleanup trap to ensure postgres branches and endpoints are destroyed
after tests complete, preventing resource leaks.

## Test plan
Run affected acceptance tests:
- `go test ./acceptance -run
TestAccept/bundle/resources/postgres_branches/without_branch_id`
- `go test ./acceptance -run
TestAccept/bundle/resources/postgres_endpoints/without_endpoint_id`

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: pietern

acceptance/bundle/resources/postgres_branches/without_branch_id/script

@@ -1,5 +1,10 @@
 envsubst < databricks.yml.tmpl > databricks.yml
 
+cleanup() {
+   $CLI bundle destroy --auto-approve > /dev/null 2>&1 || true
+}
+trap cleanup EXIT
+
 trace $CLI bundle validate
 
 # Deploy output differs between engines, so capture to per-engine file only

acceptance/bundle/resources/postgres_endpoints/without_endpoint_id/script

@@ -1,5 +1,10 @@
 envsubst < databricks.yml.tmpl > databricks.yml
 
+cleanup() {
+   $CLI bundle destroy --auto-approve > /dev/null 2>&1 || true
+}
+trap cleanup EXIT
+
 trace $CLI bundle validate
 
 # Deploy output differs between engines, so capture to per-engine file only