Rename migrations package, to match goose generated migration files

db/migration/20200508093059_add_artist_song_count.go

@@ -1,27 +0,0 @@
-package migration
-
-import (
-	"database/sql"
-
-	"github.com/pressly/goose"
-)
-
-func init() {
-	goose.AddMigration(Up20200508093059, Down20200508093059)
-}
-
-func Up20200508093059(tx *sql.Tx) error {
-	_, err := tx.Exec(`
-alter table artist
-	add song_count integer default 0 not null;
-`)
-	if err != nil {
-		return err
-	}
-	notice(tx, "A full rescan will be performed to calculate artists' song counts")
-	return forceFullRescan(tx)
-}
-
-func Down20200508093059(tx *sql.Tx) error {
-	return nil
-}