db: Refactor switch; NFC

internal/db/paste.go

@@ -73,11 +73,7 @@ func ErrHTTPStatusCode(err error) int {
 	switch err {
 	case nil:
 		return 0
-	case ErrKeyInvalidChar:
-		return http.StatusNotFound
-	case ErrKeyInvalidLength:
-		return http.StatusNotFound
-	case ErrPasteDoesNotExist:
+	case ErrKeyInvalidChar, ErrKeyInvalidLength, ErrPasteDoesNotExist:
 		return http.StatusNotFound
 	}
 	return http.StatusInternalServerError