docs(migrating_to_8): fix no ending-new-line (lint)

Author: hasezoey

docs/migrating_to_8.md

@@ -59,4 +59,4 @@ Use `findOneAndDelete()` instead.
 <h2 id="removed-id-setter"><a href="#removed-id-setter">Removed id Setter</a></h2>
 
 In Mongoose 7.4, Mongoose introduced an `id` setter that made `doc.id = '0'.repeat(24)` equivalent to `doc._id = '0'.repeat(24)`.
-In Mongoose 8, that setter is now removed.
+In Mongoose 8, that setter is now removed.