fix: address code review findings (consolidate slice helpers, correct bootleg comment)

internal/musicbrainz/sync.go

@@ -152,18 +152,6 @@ func SyncArtistDiscography(
 	return releases, nil
 }
 
-// hasSliceType reports whether the slice contains the wanted value. It mirrors
-// hasSecondaryType in api.go but operates on the persisted []string form read
-// back from external_releases (cache-hit path).
-func hasSliceType(types []string, wanted string) bool {
-	for _, t := range types {
-		if t == wanted {
-			return true
-		}
-	}
-	return false
-}
-
 // getArtistFilterOptions reads per-artist type filtering preferences.
 // Defaults to no filtering if artist_settings row doesn't exist.
 // artistID is the Navidrome artist ID (artist_settings.id), not the MusicBrainz ID.