Fix issue with MariaDB/MySQL migrations (#3994)

MariaDB/MySQL doesn't like the normal `"` quotes around the column name.
This needs to be a backtick **`**.

This PR changes the migration script to fix this issue.

Fixes #3993

migrations/mysql/2023-10-21-221242_add_cipher_key/up.sql

-ALTER TABLE ciphers 
-ADD COLUMN "key" TEXT;
+ALTER TABLE ciphers
+ADD COLUMN `key` TEXT;