Currently <script blocking="render" type="module"> requires a `src` attribute, even if this `src` is a data URI. This is an unnecessary constrain, as inline module scripts that import other script should still be able to render-block. See https://github.com/whatwg/html/issues/10034
This is a small change that removes an artificial limitation from <script blocking=render>. The motivation for this is that cross-document view transitions often rely on render-blocking scripts for customization, so making render-blocking scripts easier to author would support this feature.