Removes leftover Magic Mushroom database (#4634)

* Removes leftover database from YAML conversion.

db/import-tmpl/magicmushroom_db.txt

@@ -1,8 +0,0 @@
-// Magic Mushroom Database
-// List of skills that are randomly used through Magic Mushroom status change.
-//
-// Structure of Database:
-// SkillID{,RemoveFlag}
-//
-// - To remove entry by importing, put 1 value on 'RemoveFlag'
-