Fix migration

Signed-off-by: Arthur DANJOU <arthurdanjou@outlook.fr>

database/migrations/1625330080117_guestbook_messages.ts

@@ -4,8 +4,7 @@ export default class GuestbookMessages extends BaseSchema {
   protected tableName = 'guestbook_messages'
 
   public async up() {
-    await this.schema.table(this.tableName, async (table) => {
-      await table.dropColumn('message')
+    await this.schema.table(this.tableName, (table) => {
       table.text('message')
     })
   }