fix(bridges): fix default value for enable when attempting operations

[thalesmg]

Fixes https://emqx.atlassian.net/browse/EMQX-11999

Although the frontend doesn't send enable when creating a bridge/action/connector, the default value in the schema is true, so when attempting to fetch it from the raw config we should adhere to that default.

Release version: v/e5.6

Summary

PR Checklist

Please convert it to a draft if any of the following conditions are not met. Reviewers may skip over until all the items are checked:

• Added tests for the changes
• Added property-based tests for code which performs user input validation
• Changed lines covered in coverage report
• Change log has been added to changes/(ce|ee)/(feat|perf|fix|breaking)-<PR-id>.en.md files
• For internal contributor: there is a jira ticket to track this change
• Created PR to emqx-docs if documentation update is required, or link to a follow-up jira ticket
• Schema changes are backward compatible

Checklist for CI (.github/workflows) changes

• If changed package build workflow, pass this action (manual trigger)
• Change log has been added to changes/ dir for user-facing artifacts update