Remove invalid migration

db/migration/20201025222059_purge_cache.go

@@ -1,25 +0,0 @@
-package migration
-
-import (
-	"database/sql"
-	"os"
-	"path/filepath"
-
-	"github.com/deluan/navidrome/conf"
-	"github.com/pressly/goose"
-)
-
-func init() {
-	goose.AddMigration(Up20201025222059, Down20201025222059)
-}
-
-func Up20201025222059(tx *sql.Tx) error {
-	cacheFolder := filepath.Join(conf.Server.DataFolder, "cache")
-	notice(tx, "Purging all cache entries, as the format of the cache changed.")
-	return os.RemoveAll(cacheFolder)
-}
-
-func Down20201025222059(tx *sql.Tx) error {
-	// This code is executed when the migration is rolled back.
-	return nil
-}