fix: commit regardless of framework's transaction_writes count

[ankush]

• There is code that depends on "commit", everything that happens with db.after_commit.
• There are operations that will not write anything to DB but just
  enqueue the function, if it's enqueue_after_commit then it will break.
• Empty commit/rollback both are basically free. MySQL treats transaction as read-only until a write is made.

[ankush]

This can break code like this:

@frappe.whitelist()
def enqueue_job():
    try:
        frappe.enqueue("job", enqueue_after_commit=True)
        1/0 # Any exception really
    except Exception:
        pass

Previously this job was not queued because we didn't see any writes hence no commit.